I have been installing for several years now and I have found that 6 ga. Aluminum copper aloy wire seems to work best as power cable for both efficiency and and resistance to degrigation!
Also I run 2 ground cables 1 from batt to amp neg terminal and to second from body of vehicle to body of amp this really helps with keeping amperage consumption down thus alowwing for cooler temperatures. Also use #6 lugs for cable terminations at batt and body. Also I use an rf filter on remote cable using #12 cooper in order to reduce ac hum from alt. If you can afford to do this it is highly recomended as I have had no issues with any amp to include temperature issues and have never upgraded a batt / alt or installed a cap!