I think what curegeorg was alluding to was tonal balance, speakers that are the same or at least are from the same company and share the same tonal qualities so that as a sound moves around the room it's not changing it's tonal quality from speaker to speaker. (if that's not right be sure to let me know curegeorg)For instance all 7 of my speakers are Boston Acoustics, VRM-50's mains, VR-12 center, VRS Pro side surrounds and Micro 90's for back surround.
As for an upgrade from your BIC center, that's a tough question. What you really need is a local dealer who will let you take home different center speakers and auditon them with the Legacy's. I would try the lower end B&W's they are great speakers and more reasonable than you think, I also think that they would be a pretty good match with the Legacy's. Good luck and happy shopping.

[This message has been edited by shawnb16 (edited June 04, 2004).]