Any amp would be good enough to drive the sub since it is only taking a line level signal. The EP800 does the amplification. A +8 setting on the receiver seems way to high to me. The amp could be distorting the line level signal at this level of gain.

LFR1100 Actives,QS10HPx2,QS8x2,EP800,M3x4,M3x2 (Wood),M5HPx2 (Wood),AxiomAir,ADA1500-8,ADA1500-7