You may know this, but I thought I'd better mention changing your 15 Amp outlets to 20 Amp outlets does not give you a 20 amp circuit- not without a 20 amp breaker and, I believe, minimum 12 gauge wiring in the circuit. Besides, you will probably want your 20 amp circuits to be dedicated to your amps. Good luck!
By the way, Ed, are you saying the 2 Earthquake Cinevova amplifiers (6 total channels) are less money than the 770 (7 channels)? These are new?