You have a 7 channel amp, try bi-amping your mains and see if it helps. Personally, I think you will see the most improvement in clarity by matching your front three speakers. I'm not knocking mac or def tech, they all sound better by matching all 3 fronts.
Don't bi-amp mixing the Denon and Mac. I would try using the Mac just to power your front 3 speakers.
Don't bi-amp mixing the Denon and Mac. I would try using the Mac just to power your front 3 speakers.