best way to judge an amp is by checking its input power usage
an AB MOSFET amp has an efficency of about 50% or less, if it consumes 500watts from the battery, it only will be producing about 250watts at the outputs. so HOW to check how much power ur amplifier draws from the battery? Well check the fuse fixed on the amp itself, thats the maximum current ur amplifier will be drawing continuously when driven hard. ur wires should be able to withstand that.
the 600w figure u posted, i beleive is peak value,
it will have about 200watt continuous RMS at outputs, by usuing about 400-600watts from the battery, with 12volt battery, current == 400/12 =~ 35amperes,
see on ur amplifer, it will have two 20A fuses i beleive
from the above chart, use a wire safe for 40A, ( for continous extreme conditions ), for normall conditions, u can get away with half the wire size.
for fuse, i beleive, amps have there own fuses, what im usually varied is the wire catching fire, u should use fuse equal to maximum load capacity of the wire.
best place to fix it is close to the battery, but it gets very hot, so i shifted mine to diggi/dikki
if u listen at moderate volumes, just get a fuse, else ask ur electrician to wire both amps independantly.
