according to crutchfield's description for that amp:
the easiest way to determine the necessary wire/fuse size is to look at the fuses that are on the amplifier itself. in this case, that amplifier has three 35A fuses, so your power and ground wires should be able to safely handle at least 105A (4AWG is the most common wire thickness available that can handle that much current).
4-gauge power and ground leads with 150A ANL wafer fuse and holder recommended
your fuse rating should be higher than what the amplifier will draw, but lower than what the wire can handle. crutchfield "recommends" a 150A fuse because they don't sell any size between 100A and 150A in that fuse type (ANL)