Kitsune Holosprings 3 Dac vs Luxman L507z

Hello,

I'm using these together via XLR cable. The DAC output is 5.8 volts and the Luxman accepts max 6 volts into the XLR connection PCM. Am I in danger over overdriving the amp? Ive done A/B testing using an RCA cable also. Output is lower but isnt as bass heavy as with the XLR . RCA DAC output is 2.9 volts.  Am I losing any quality using the RCA. The run is 3 feet or so.