You should also try FW 1.2.7. When I 'upgraded' from 1.2.7 to 1.3.5 the sound quality when using with my AKG K3003's went downhill for me, vocals sounded like they were just on the point of clipping and this made me roll back to 1.2.7 which is a perfect match for me. Worth a try. Note that whenever you change FW it s a good idea to do a reset from the settings menu (does not wipe your music)
Also, as others have stated in this thread, there is no real WOW factor to this DAP. The sound it produces is exquisite, just spend some time with it, you'll see.
I've had wow factors though with this DAP. Particularly in the bass department ;).