I can't see the comment above me, because John is an idiot and I've blocked him. Whatever be said, though, just ignore him. He has no audio knowledge. You're better off blocking him, too. The majority here will likely agree.
To the subject at hand, you'll get the best recommendations if you can at least give us that length, width and height of the maximum area you're willing to give up for the sub, as well as a ballpark dollar amount for sub and amp. Cheap to some is