It might be the same type of material but I don't think those are the same items. The 3Rivers images don't match up with the Minus33 stuff I own at least, so other than the material they're made of, I can't speak to the quality of the 3Rivers items. I do have a few Minus33 pieces, but I only use them for base layers because I find them rather thin and they only come in rather dark colors (suitable for blinds, but not for sitting out in the open).
At those prices, I would also consider First Lite (I have a FL quarter-zip Chama and an 'Expedition' weight Minus33 full-zip -- the FL item is much thicker, warmer, cheaper and 100% Merino wool).
Also, look at Kuiu for lighter weight layers; good prices, excellent quality (only issue here is that their camo pattern items are frequently backordered, though they offer some excellent solid colors for hunting as well).
Edit: Wanted to add that in the past, I've had excellent luck raiding thrift stores for cast off Wool items, especially sweaters, many in colors/patterns perfectly suitable for hunting. Nothing like sitting on stand while toasty warm in a $5 merino wool sweater.