Maybe I just sweat more than most but I found that the sitka base layers stink and after a couple days I couldn't stand myself. It was so bad I had to wash them in the creek every 2 days. I went to firstlite merino wool base layers from asat and solved that problem.
I haven't tried the 90% lineup, a medium pant is to small and a large to big. I do own 2 pair of the ascent pants and in the heat nothing compares. These babies really breath well and keep you cool. But with that breathability comes a complete lack of wind resistance. So I keep a rain proof shell handy in case the wind kicks up and the temp drops. I will probably try out the new pant with the knee pads. The ascent pant is not real tough and I popped a hole in a 30 day old pair last yr that I had to have repaired. To much sitting around looking thru glasses I guess.
I had the celsius vest and for warmth you can forget it, at least imo. I replaced it with the kelvin jacket, its warm and blocks the wind too. The sleeves fit tight so no worries about the bow string. Packs up just as small as the celsius vest. If it rains/windy/cold/snow gets nasty, throw a shell over that and you'll be snug as a bug in a rug.
I do have some of the apxg2 but pant wise I don't like the fit. Base layers fit well but for warmth the L3 is to light, haven't looked at the L4. They also have sizing issues imo. The L1 fits a little loose but the L2 fits tight, seems like it should be the other way around to me. I'd actually like to get rid of the stuff if I could. Besides, I think a 3 layer system is really the way to go and I get that with merino wool base, ascent/kelvin, waterproof shell.
By the way, goretex bought sitka last yr.