RE: under armor- worth the money?
You will not find a better wicking material than Under Armor (Polypropelene) We use it here in the Coast Guard as part of a 3 layer system. polypropelene, then a fleece body suit followed up by a dry suit. I can jump in 30 degree water and stay nice and warm for hours. Of course you wont be wearing a dry suit but a good set of winter hunting overalls or bibs/parka will do nicely. Dont forget 90 percent of your heat is lost out of your (unprotected) head and grion/armpits. Buy a good hat to wear and you should be all set.
You can get fleece body suits thru mustang survival or polar tec
Hope this helps
Mack