DAC is different, so it'll sound differently. From my experience, the different amp modules also changes the sound enough to be noticeable. Also the Q1ii may not have enough power to drive your HD600 properly. I own the Q1ii and the AM3A module on the x7ii (same one on the Q5) and I can tell you that via balanced on both, Q1 can drive the 300ohm beast at about 60%~ while the AM3A can go about 80%~ on my HD650. If you switch the AM5 high powered module then you'll get even better output for HD600.