Speed ped, regarding running OVERCURRENT: Just cause it CAN be done, doesn’t mean you should go around recommending it.
Its unsafe (as in: beyond rated) and therefore stupid when there are much better alernatives readily available. Kinda like cutting coil springs because you’re too cheap to buy a set of lowering springs.
unless you run the amp into square wave constantly you’ll most likely be fine on 8ga. what load are you running the amp into? Class AB amps are generally 60% efficient, @ 400W you’re prolly not drawing more then 50A.
sheesh, if it was 50A through 8ga wire… your gonna drop a fair amount of voltage running 8ga… 4ga power and ground is the way to go by far, I bet you can hear an audible difference through the speakers if you had it cranked up on the 4ga vs 8ga wire. If the routing sucks, see if you can do 2 runs of 8ga, that should be fine