Are you trying to go cheap (but reasonable in weight) or UL (hang the cost)?
My snarky response to Caliornians & Oregonians dealing with sub-zero temps for the first time (I was once was one such person):
"If you get cold, you're used to putting on a sweater. When it gets really cold, you put on a jacket. When you're still cold, you just might realize you need to put on a hat. But you've been wearing the same pants the whole time."
I said that a lot while working in a coastal California BPing store.
That you have capilene bottoms is a good start. You probably don't have as many layers for your legs as you do for your trunk. And, at least as much as for your trunk, the outer layers need to be bigger than the inner ones. The cheapest way to go is with "powder pants" or "ski bibs" for as little as $39 at a sporting goods warehouse store. Or STP:
http://www.sierratradingpost.com/marker-gillette-ski-bibs-insulated-for-men~p~14729/?filterString=s~ski-bibs%2Fclothing~d~5%2Fmens-clothing~d~15%2F&colorFamily=27
take off another 30% and it's $39.
There are other bottom layers you may already have and wool or polyester pants do well in the cold. Even retired dress pants (more layers of those, though). $5 at a thrift store. Also, as a West Coaster using dealing with liquid water, it is easy to forget that there is no liquid water at -10C/14F. So you CAN wear cotton jeans (flannel-lined, better yet) or sweat pants, as long as you don't sweat in them or fall in a creek.
For gloves, downhill skiing gloves work well in low temps. Wool or polypro liners let you adjust them a bit to warmer and colder temps. Also, liner gloves let you make camera adjustments without exposing your bare skin.
Footwear is another arena that needs different gear but you can't just "layer up" as easily as you can on you legs and trunk (there are some insulated gaiters, through). Sorels are the classics, but Kamik and Khombu aren't so spendy. Here's a $30 option (after taking another 30% off):
http://www.sierratradingpost.com/itasca-benchwarmer-pac-boots-waterproof-insulated-for-men~p~7364j/?filterString=s~snow-boots%2Fshoes~d~4%2Fmens-footwear~d~11%2F&colorFamily=01
Hats can be layered and a thin fleece or wool skull cap can be used by itself, as can something with more coverage (chin flaps) or they can be used together. You may not know about neoprene face masks, but those help a lot below 0F or if there's much wind below 20F. Walmart, REI, and Sportsmen's warehouse all have the $25 ones. I've found slightly thinner (therefore lighter) ones on ebay for $1.50 – $2 each including shipping and my kids use them down to about -10F/-23C and use the thicker ones below that.
http://www.ebay.com/itm/Neoprene-Neck-Warmer-Warm-Face-Mask-Cover-for-Sport-Motorcycle-Bicycle-Biker-/251561840525?pt=US_Athletic_Clothing&var=&hash=item3a92410f8d
-10C sounds pretty conservative for the Rocky Mountains in September unless you're going very high. Possibly, certainly, but not common. Banff shows an average Hi/Lo for October (!) of 48F/29F although record Hi/Lo of 79F/-7F