Hi John:
At a minimum I would step up to the XMP100 but driving two pair of 8-ohm speakers sounds more like the AMP200 a Class AB High Current Power Amp that is 2-ohm stable. There is no drop off using a 3.5mm RCA to dual Male RCA adaptor cable. Its always better to have more than enough power available in your Power Amp. You will really notice a difference at quality at lower volumes (aka. background music).
TL/12/7/20