I have a set of Duofold and Under Armor. The Duofold were about half the money, and IMO they are also warmer. They are made with Merino wool and wear well. Just don't put them in the dryer. I've had the Duofold for years, so I don't remember where I bought them, but I'm sure you could just to a search to find sources.
AIRASSAULT
PMA Member
You should be able to get the Polypropylene's at a Military Surplus store pretty cheap. I've been using my polypro's that were issued to me and they work great for hunting.