I dont have any 8 ampers around so I think I`ll leave well enough alone for now, I dont want to be blowing this thing up so soon!
I just took some more measurements, line voltage compensated with the variac. The figures I got before were on a heavily taxed circuit hovering around 110v. With a 120v line voltage, this thing is putting out 481wpc at clipping into 8 ohms
I had to readjust the meters as they were really off. They are much more accurate through the power range now but need to be further tweaked to indicate clipping.