Mike, we have similar tastes in external amps. The X5 however sounds great from the headphone out. The sound is clear, smooth and authoritative. I am convinced that the plethora of power is a big reason for the last quality.
You pay for it somewhat: a large heavy internal battery producing about 10 hours of play. Still, the X5 is quite thin with a nice form factor. Compare that with adding a Quickstep to another DAP... you are way ahead of the game and the sound quality is excellent.
Me thinks that you will like the X5. :-)
Edit: These observations are all with IEMs: Heaven VI, Kaede, 1601SC and 1602SS. Full size headphones are a different story always but since I don't use them with DAPs, I cannot comment. It is fair to assume though that the X5's power will be very useful.
Edited by cooperpwc - 1/28/14 at 9:44pm