hifonics amp

I've got a Hifonics ZRX600.4 (75 watts x 4 @ 4 ohm) running to a set of Kicker KS6.2 components (75 RMS/150 peak) and Kicker KS69 rears (150RMS/300 peak) running off of a Pioneer AVH-X1600DVD Head Unit with 2v pre-amp outs. Issue: To tune, Hifonics support told me this is a "peak power" amp...

I know a guy selling a hifonics xx zeus amp for super cheap..... Dont know what year these amps came out but the retail is something retarded like $800. Did these amps do rated and what do they compare to. I would guess they are better then the new ones becuase they are rated with rms instead of...