Yeah, Tamron is a pretty good brand. The difference is just glass quality, and construction. You want the highest quality of glass, because lower quality glass will decrease your picture quality. The better glass will do that too, but not so much. (shooting through layers of glass and air, so you want the clearest you can get).
Just try to stay away from anything that looks too good to be true. Quantaray isn't that great, but then again, I use a Quantaray UV filter because its cheap. On something like a polarizer though, you really don't wanna skimp, so go with something a little nicer.