My friend is curious, and I told him I'd ask.
Setup 1:
400 Watt MA Audio Amp
300 Watt RMS MA Audio 10" Sub
Setup 2:
400 Watt Sony Xplod Amp
Two parralel 395 RMS Sony Xplod Subs
So the first sub would be running with 300 Watts, the second would be getting ~200 Watts each, for a total of 400.
Would there be much of a noticable difference?