MaxCast brings up a good point about center channels I forgot to mention.
The center channel is THE most important speaker in a multi-channel movie setup. Pick a quality center that sounds as life like to you as possible. Then get mains to match the center, or identical speakers if possible.
IMO the importance of speakers falls into this order, first being most important, last being least. Center, Sub (or better yet subs), Mains, Rears, Rear Centers.
I don't feel that any sub that makes a loud boom is fine for HT use. I read too often about a sub that someone thinks isn't ok for music because it's flabby or muddy or boomy etc., but they feel is suited fine for HT. Why do people feel that muddy subs are fine for HT as long as it's loud?
When I was testing subs, I was using the Mini-Gun scenes from Predator, T2, & The Matrix. Had no problem picking out the subs that didn't work for me because they weren't tight enough.