Anyone Using Outboard Dac with Marantz AV7701

Anyone using an outboard dac with 7701? I tried the Schiit Gungnir without success. I'm not into headphones. BD's, Apple TV, internet radio, CD's via BD player. I was looking for greater sound stage and diffinition. I achieved it with movies but not music or TV no matter the source I heard no discernable difference in SQ. If you have experience with this please advise how you connected, dac of choice and general experience. Equipment: AV 7701, MM 7055 amp, Emo XPA-100 monoblocks for mains and center, B&W 683, HTM61, B&W 684. Apple TV, Sharp BD, Cable box. Originally had the dac with xlr into prepro - no joy. Jason at Schiit suggested I connect to the amp, at this point I achieved the aforementioned in SQ playback. Final setup was: Gungnir via xlr into amp MM7055, Apple TV via optical, RCA into BD and cable box.