I'm looking at making one last big purchase in the way of speakers before I go back to school full time. I currently have the standard ProCinema 100 set, except with a ProCenter C2. My question is, what single upgrade out of BP6 towers, BP8 towers, or a new center channel would give me the most benefit? I'm trying to keep cost down, so I'm also especially interested in how big the difference is between the BP8's and the BP6's. Any and all help is appreciated. Thanks.