I have yet to hear a planar that I really enjoyed, though the HE-500 is not bad, still have it. Audeze never floated my boat. Did you ever hear a Denon AH-D5000? I see you have the D600. Some say the D600 is not quite as good overall as the D5000 or D7000 was. Then again the TH900 should be better, right? I've heard the TH900 but not A/B with the D5000.

My D600 is super comfortable but the sound is a large step back (I only use mine at work) from the older Denons like the D5000 (these older Denons were actually made by Fostex).  Yes the TH900 is noticeably better than the D5000, IMO.