Go north to Boulder, you'll find several places worthwhile for your UL pursuits.
#1 Montbell's store: if it's UL and sometimes a bit wacky, it'll be there.
#2 REI (in denver, westminster, boulder..etc) Ok, so really it's not UL specific but there are SOME items that fit our pursuits there and the Denver flagship is just a darn good store.
#3 Golite Warehouse Sales (Boulder) - sign up, go to them. You'll be pleasantly suprised.
#4 Neptune Moutaineering (Boulder) - Quite a variety, seems to carry items that were hand picked by people who actually hike/climb/watever unlike stores that usually focus on what they think they can fill someone's pack with. Still, not strictly UL, but worth mixing it up with after you've tried REI.
#5 Bent Gate (Golden) - better for climbing gear really, but they're a good store too.
#6 North Face (Boulder) - Uh, well it's worth mentioning. Nearly zero UL, but if you need poser clothes that double for more than just hiking, they do have an outlet store just a hundred feet from Montbell.
#7 Holy-Hell-All-of-The-Bulk-Food-Places - You're gonna need to eat. Go to one of the hundreds in the area to stock up on the stuff to pack your own meals.
A lot of gear companies are actually located in the Denver/Boulder area, sometimes you can look them up to see if they have any 2nds worthwhile. Everything from Thule, Golite, Trek, Trek Light (hammocks), Trango, Black Diamond - and even my company, Slackline Express.