I agree with Sean. I would like to add that if you have many listeners and therefore all can't be in the sweet spot, off axis listeners might enjoy the center channel. I also strongly believe that all chanells should be as similar as possible and equidistant from the sweet spot listening position.
Try 4.0 or 4.1 instead of 5.1... it's worth a shot
I just had something I wanted to run by everyone.I was tweaking some on my system and I noticed I got a much better soundstage from setting my center channel processor to "off". I'm not even using a subwoofer...not by choice though.I am now convinced with several trials that not only do I not need a center channel, it actually screws things up due to EQ problems.I have tried this on several set-ups and it was true every time.As silly as it seems I urge everyone to try it.I am using Thiel cs1.5's with h/k avr510 htr.pioneer dv-47a dvd-a/sacd/dvd player and toshiba 65hdx82 rptv.