center channel Preamp/Amp setup help needed

I have a Sony TA-E9000ES PreAmp. It has two center channel preouts. I want to connect this to separate stereo amp for center speaker (Polkaudio LsiC). My amp is a Yamaha M-40 which has one input channel and two sets of speakers out (A & B).
1) How do I connect my preamp to main amp? center out from preamp to Left (or right) of amp? Can I connect one centerout from preamp to L and the other ceter out of preamp to R of amp?
2) Center channel uses only one side of the amp's speaker out. Is it harmful to the amp to leave the other side unused?
3) The LsiC center speaker can be bi-amped and bi-wired. What is the best way to setup this system given the above preamp and amp units?
4) I looked at some Yamaha professional power amps on ebay, such as Yamaha P2500 Pro Series Power Amp. Can this kind of unit be used for center channel? How are these kinds of amp different than HT(Yamaha M-40) amps? better or not?
Here is the units I own:
Sony TA-E9000Es PreAmp/Processor
Yamaha M-60 for fronts, Yamaha NS-1000 speakers
Yamaha M-40 for surrounds, PolkAudio LsiFX speakers
Need to buy amp for center, PolkAudio LsiC center speaker
Yamaha YST-SW1500, 1000 Watts powered subwoofer

Do you think this equipment is good enough for later integration of DVD Audio or SACD?