Hee hee, I just had the baritone soloist on Estuans Interius (Burning Inside) from Carmina Burana (DVD-Audio), which is entirely in the center channel with vary little musical accompaniment, hitting between 97 and 100 dB. That's the clearest I've ever heard that track. My receiver didn't even break a sweat, despite the slightly less breathing room from moving the shelf above it down (still open on all sides, so it's not a big deal).

Pioneer PDP-5020FD, Marantz SR6011
Axiom M5HP, VP160HP, QS8
Sony PS4, surround backs
-Chris