That's my current setup- I enjoy it very much! However, only thing I have to compare it to is the µDac2 (not bad either). They are fairly easy to drive, though not as easy as my V-moda M-80s or my M50s.
I see earlier that you asked about the Audioengine D1. It is, indeed, an excellent value and I am currently running my 600s from it- haven't listened to anything that the dac/amp combo couldn't handle extremely well. Much better than my motherboard! Highly recommended.
I call BS OR he is retarded- you will not regret getting the M80s. I own them as well as the Sennheiser HD600s and while the 600s are better sounding, the M80s are more versatile and sound pretty damn good! I listened to the Solos and my M80s side by side and it wasn't even close- Solos are crap! M80s are better than the Studios as well. The Pros do sound pretty good compared to the M80s, though it is close.