A former boss was an audiophile with varied amps and headsets. I tested, then backed up my pick with reviews from this very forum over a decade ago. My 650 is still my daily driver and it doesn't mind cheaper amps from FiiO. I have been using an E12K MB and sometimes an E10K for specific applications. I found I don't require a fantastic amp as I can combine with PulseEffect profiles and convolutions. I'm nothing but delighted with the range of this headset. Balanced bass, crisp vocals, clear instrumentals, and it doesn't skip a beat on busy pieces...