Look into Memphis Car Audio. They make some of the best quality subs I have ever seen, I used to own a few of the M3 12"s and M3MOJO 12"s. I've never seen anyone have anything negative to say about them. The Mojo line is probably a bit of an overkill for what you are looking for, but a standard M3 or even a PR series would probably suit you well. They are not $20 subs but are not as expensive as your typical mainstream subs either. I'd say quality and sound wise they outperform just about every mainstream sub I have seen with the exception of a few that are very high dollar (w7 for instance).