Depending on your Front speakers you maybe better off without a Center channel. With my speakers the Center channel restricts the power delivered to my Fronts. My Fronts are capable of bridging the center gap and deliver full power, however my setup uses reflected sound due to my narrow room. So I have the Center channel switched to Off.
What I'm also doing which you can do as well is I have my balanced outs on the SP2 connected to a Yamaha MG-10 mixer balanced Ins, then connected the balanced outs on the mixer to your balanced ins on your amps. This mixer has low enough distortion .01 so it won't mask the sound, at least I can't tell. The mixer will also give you better control of Line Level, Gain, tone control, volume. And I find the sound quality to be more refined. The mixer is capable of being a pre on its own but coupled with the SP2 I think it sounds great. With the mixer though you only get stereo, I use 2 sets of speakers for 4 channel stereo.
That's all that I can think of at the moment.
