I’ve got a Icebreaker GT 260 Rapid Leggings (Size S = 223 g) and a Bodyfit 200 top (Size S = 190 g) and they’re good quality. I haven’t worn them yet a lot, so can’t give you deep insights on them. However, I have worn my Woolpower 200 long johns and long sleeves very much, and they’re really excellent. I also own a Smartwool Microweight Zip T and long johns and also value them very highly.
I wear both of those sets in the 0°C till -30°C range and am fine in them, although extra insulation in really cold weather is always welcome, so you might be better off in the Icebreaker 260.
So in case you’re looking for us to allowing you to go shopping, please go ahead, you’ll enjoy the comfort and warmth of your new merino underwear!