Matt;
IF you are already using decent 12AWG cable, don't waste your time biwiring, especially for the rear speakers. You will throw unnecessary money away on cable, make your setup more cluttered, double the capacitance load on the amp, and achieve no real audible benefit. Biwiring is one of those unnecessary tweaks provided you are already using decent cables to begin with. Focus more on speaker placement, proper calibration and room acoustics as you will get more mileage for your money.