After spending some time between the two players last night, I think this comes down to how much power you need / what kind of signature you prefer. C3 is the colder sounding player, it won't have a beefy low end like the Hifiman, it has the most clarity of the two, it also has the airy wider stage. Instrument separation is about even, if anything they just express it slightly differently, HM-601 expresses separation with ease without being overly obvious which blends into the presentation well, while the C3 can sound a little clunky at times compared. it's a little in your face. I do believe HM-601 has the better micro detailing and stereo of the two. I enjoy them both, but I can see HM-601 as a player that may not wow everyone straight away. It's warmer natural and more analogue sounding, which I really enjoy. C3 still has that digital sound signature, which can sound a little fake but jumps out and says "hi" The Hifiman has over double the power even on low gain, and for headphones would be the better choice.
Both are excellent players in their own right, it really depends what kind of signature you prefer.
Another quick comparison can be found here.
I'm not into fullsize headphones but Sony MDR-V6 pair well with C3.
If you have any questions on pacific area's betwwen the players I'm happy to help. Basically though, with these two choices cross the Cowon off your list imoEdited by H20Fidelity - 1/29/13 at 2:23am