I just set up a pair of 604-8Gs (in parallel) as a center speaker between a pair of Olympus S7s fronts. The receiver is a Sony DA3100ES 7.1 with 100 watts per channel. TV, DVDs and DTS discs all sound absolutely amazing.
I have a single Heil AMT-1 tweeter that I'm going to hook up to the Altecs and I'm sure that it will be an improvement but there's no obvious lack of high end.
The Altecs are cut 3db to match the JBLs and I have Infinity rears that are boosted 6db. They are OK for movie effects but really don't match up with surround music and I'll replace them soon with a pair of Valencias or 604Es that are sitting in the garage.
I have a 12" 300 watt sub that is disguised as a cherry wood end table that sits against a wall with DVDs stacked on it.
I'm amazed how good the system sounds only a few feet away.
Bob Walker