Aeropostale has some really affordable polos and shirts for a very good price.
H&M for guys sounds very, very promising, however you'll need to go see if there's an H&M near you that sells guy clothes. Their clothes are very affordable and good quality, as well as really cute.
And I hear Old Navy's got some really really great stuff now, even though I don't really shop there, but I'll probably go check it out. c:
Department stores are always pretty decent.
Places like Marshalls, Kohls, TJ Maxx, Ross, have some really nice stuff. I haven't been to them in a while though.
Good luck~