I think the bx8s are well-worth the close out prices they are going for. I picked up a pair for only $279 from MF. They weirdly marked them back up to $299 like a week after I bought them...
I'm VERY glad I went with the 8" speakers though. The GC salesman sold me on the 8"s when I went in to demo a pair of rokit 5s. I know he was just trying to get to spend more dough, but damn, he was right about being able to hear the bass, and the bx8s can pump out the bass.
I can't comment on any other models since the bx8s are the only ones that I'm familiar with, but the larger speaker will make a BIG difference. M-Audio stuff seems to get good reviews, so I'm sure you could do worse than the bx5s or dx4s, but like i already said, having that bigger sound from a bigger speaker is worth the extra cash IMHO.