Holy $h1t, just got the Shiit Stack today with a new pair of AKG K712. I am so glad I went with this instead of the X2s. The bass, clarity, soundstage is all amazing. I tried out my DT 770 pro 80 with the stack and it was ok, trebles are a little sharp but very clear and detailed. The HD 598s sounded amazing as well, definitely brings out the meds well. I would say the K712s are the best of both worlds, happy medium between the two. Great bass, soundstage, clarity and treble. I honestly think I am done with headphones, I found the pair that's perfect! And did I mention comfort? AKG is the best!!!!!!!! A lot more comfortable than the 598s or the 770s
Enjoy the music!