Talk me out of these (Six Moons, Therm-a-rest)

First, yes, return or otherwise unload the BA items.

Slow down on replacing them.

What about the Luna Solo appeals to you?

What position do you sleep in? XLite has great specs, but I found the standard size too narrow as a side sleeper.

I think you're right that the NeoAir X-lite is just about the gold standard. The only consideration there would be that some prefer closed-cell foam (CCF) pads. They aren't so comfortable (obviously people vary widely in their opinion of how much less comfortable they are), but they are bulletproof – can't puncture and no inflation hassle. But CCF pads are cheap anyway.

I don't know the Six Moons tent specifically, but in terms of your "upgrade" worry — I think, essentially, that the question would be whether you want to pay up for Cuben Fiber. For example, a Z-packs Cuben Fiber tent would be half the weight, similar or better functionality, but over twice the price.

If you don't want to pay up for Cuben Fiber at this stage, it would seem sensible to stick with a widely-used classic from a thriving company that will lose little in value if you sell it in a year in good condition. An MLD Silnylon Mid might be the first thing that come to mind in that respect.

I wouldn't worry too much if 40L might be overkill or not. I tried using smaller backpacks too but always ended up annoyed because packing was a pain on the ass. Ultimately, I switched back to my Golite Jam for all trips involving sleeping outside. Sure, a smaller backpack might save a few oz. But the increased fuzz with packing and the costs to own two backpacks kill the deal for me. In my opinion, having one reasonably sized and weighed backpack suffices until one wants to become veeeeery serious about saving the last possible ounces.

First off, buy a pack last.

As for selling stuff, it happens. $40 is nothing. As you learn more about yourself, you find that your gear needs change. It's a small part of the fun of hiking (unless you're John Muir). You might pick up that Neoair and find that you hate it. Maybe you won't like the tarp either and you'll want to switch to a bivy sack. You'll only know once you get out and use the gear.

What are your priorities?
Weight?
Cost?
Comfort?

I've never slept in the Lunar Solo but it looks like a great value for the money. As far as tents go, it gets pretty expensive to drop another 8-10oz from the Solo; probably double+ the cost. You can save money and weight by going with a simple tarp and head net.

Lots of people here love the Neo Air. I've had a life long love affair with TAR's self inflating pads and I think they are a great compromise of weight, comfort, and durability. My current go-to pad is a prolite torso length pad. I throw my clothes in a bag and under my feet and sleep comfortably on my side on anything other than concrete. I used a TAR self inflating pad in the military for the second half of my career, never used a ground sheet, and never had a catastrophic leak.

Edit to add: I'm in the minority but if you're in the market for a pack, I'd buy the ULA Ohm 2.0 first not last. It's pretty spacious and carries weight well. For three season UL backpacking, if you fill it over capacity (not including bear canister), you're doing something very wrong. If you have to carry a bear canister then that modifies my suggestion to the ULA Circuit.

Katherine mentioned it too, but if you go with the Xlite, even as a skinny guy I think going with the Wide is completely necessary, whether for side or back sleeping. On my side my knees routinely hung off the Reg width, and on my back my arms hung down to the ground as well.

If you want an inflatable pad then the only way to really go lighter is to get a torso pad and supplement with a bit of foam or your pack under your legs.

The SMD is a good solo shelter. There are others that are in about the same weight class, not anything much lighter unless you either go to cuben fiber and/or to a minimalist shelter setup, which not everyone likes. SMD also has the Skyscape Trekker which is 24oz for a solo shelter but smaller.

Ultralight can lure you into obsessing over fractions of grams if you let it, so at some point you have to be comfortable to say "light enough." It's a great philosophy and many benefits to get you from a 25lb baseweight to a 10lb baseweight. But to try to go from 10lb to 8lb becomes more of a personal choice — once you get really light across your gear list you can afford an extra ounce here for comfort, and extra ounce there for budget, etc, and many accept those trade-offs because the total load is still so light. Many on this forum have a setup comparable to a full-length Xlite and the Lunar solo and are very happy with it.

So basically, if you're wondering if you are getting onto a merry-go-round of spending more and more to continually upgrade and lighten your equipment, well that certainly is possible but you have jumped pretty far ahead with your choices (many folks go through a half-dozen shelters before getting to the point where you are now).

And as others have said, get your pack last, based on your what you end up with for your other gear.

I picked up the Skyscape Trekker, which is similar to the Lunar. The main difference was that the peak is offset to give you more headroom.

That being said, I'm tall at 6'2 or so, and when I slept in this tent the mesh was still pretty "in your face" and it gave me a little bit of claustrophobia, which was new to me in tenting.

I kept the tent and moved on to other tents designed for tall folks and finally found what I was looking for in lightheart designs Solong 6. The extra couple inches and extra couple ounces really made a large difference. However, the price jump was significant at about 100 bucks. There was a few other things I liked about the solong 6 though that made the price jump easier to stomach.

SMD though is a top-rate tent. I ended up keeping it and I use it as a loaner when I talk folks out to the woods. It's easier to get people into hiking if you have some good kit that you can share. It's absolutely an ultra-light tent (anywhere that they can get by with ties instead of toggles or whatnot you'll see it, and I strongly suggest tyvek or some other ground sheet to protect the tent floor) but at least for the skyscape if the weather is nice you can roll back the rainfly and get a gorgeous view of the sky and still have the bug mesh in place. Everyone who has slept in it really likes it. Ventilation seems to be anywhere from good to "I basically slept outdoors" if you roll up the fly.

So if you're a bigun you might want to look at other options out there, specifically longer options, but if you're say 6' or less I like SMD and think you might be happy with it.

Ultralight gear is very personal. What is poplar may or may not work for you. Buy it on some place like Ebay or gear swap at a good price so if you don't like it you can sell it. If done right all you'll be out is shipping cost and you won't be hanging on to equipment that you don't want because it will be to expensive to change. As a example I bought a SMD lunar (the 24oz version) for $100.00. My Xlite was cost $90.00. If I ever decide to sell them I should get most if not all my money back. BUT IT DOES TAKE PATIENTS AND DISCIPLINE.
Good luck

I've had a very similar experience. I started with a Large TAR Prolite Plus which was around 32 oz. Towards the end of 2013 I purchased a SMD Lunar Solo LE and it is my primary shelter/tent. You can't go wrong with the Lunar Solo. The Prolite Plus was replaced with a Large TAR xlite (16 oz). I would buy both the Lunar Solo and xlite again. Also the Lunar Solo still has some room left for gear with a large xlite. You could also look at TarpTent's Contrail, but it's more $.

I recently bought an Osprey EXOS 58. It's "fairly lite" but mainly it is the most comfortable pack I've used.

REI sells Osprey packs. Wait for a spring 20% off sale. Also drop hints, whine, cajole and otherwise pester people until they give you an REI gift certificate just to make you quit annoying them.

I'm a big guy and the 20×72 Neoair is fine sleeping on my side.

The SMD Lunar Solo is a very good tent. It can be tricky to set up, in my experience. For similar weight and price, I would also suggest looking at the Tarptent Notch. Two doors, two vestibules, plenty of ventilation, double wall. If you have a large budget, the solo Zpacks shelters are excellent and weigh under 20 ounces.

They are both good choices for most backpackers going light. Are there better options? Maybe. Are there worse? Definitely.