I had a 501s and I thought it was the biggest piece of junk I've owned from Fosgate as far as amps go.. switched out to a kicker zr240 and the 240 would walk all over it and is rated half the power as the fosgate..
we already came to the conclusion that the ones before the 801s did rated or better. the ones with the S in the name were wimpy though. I know mine was.