Who's to say they would be further back? I'm not sure what mains or even center he has. I'm sure they make a bracket that will extend out. He can also mount a shelf to the wall and angle the center down.
Definantly get it above the TV and slightly angled downward if you need to. Way to low for a bedroom setting even if you could use your entertainment center. You need to get your speakers up a bit higher in a bedroom setting than in a normal room installation.
Only time I notice it off center is in pro logic and/or reg t.v., which why I switch the receiver to phantom center for that type of viewing. We're still in the remodel stage, soon the center will be above the plasma.