I love my AU-717 powering my pair of SP-5000s. I'll soon add two SP-5500s. I'm sure the 717 can do push all four, but if I were to want more power could I connect another 717 or a 919 to use as a power amp? Instead of buying an actual power amp? How would that work? Two separate volume controls? What would be the settings on the pre amp / power amp switches? I am sure this question displays great ignorance. Thank you in advance and for you patience.