I would also mention, for base layers - check out Odlo.  I believe they are European and cater to skiers and back country explorers.  It is a brand that REI carries.  As far as socks, check out Darn Tough (another that REI carries).  Darn Tough does a lot of merino wool, but, I believe they have synthetic insulated socks as well.  Another brand to check out on socks is Thorlos (REI carries these, too).

I don't think you can go wrong with the REI Co-Op brand synthetic base layers as someone mentioned.  Arc'teryx is great, but, expensive.  If you can find Arc'teryx on sale or used, definitely go for it.