I was looking to upgrade my amp from my Sony DN840 to a Denon avr-x4200. Possibly.. A Marantz sr7010. I recently purchased a Sony xbr65x930d 4K tv. I'm pushing 2 klipsch rf 28 fronts, 2 klipsch rb 61 rears and a klipsch 5.25 inch center. The 12 in klipsch sub I don't use unless for music or movies. Should I be looking at an amp and a "pre amp"??? I see people using the receiver to push the fronts and a separate pre amp for the rears and center !?!?! I am completely ignorant when it comes to this stuff. So all help is appreciated!!