I'm pairing the new Fostex THX00 with the SEX and it sounds great. Since these are 25ohm headphones, I'm using the L-Pad I built--I described that build in an earlier thread--allowing me more usable range on the volume control. The L-Pad also gets rid of the hum I hear with these headphones. Note that with the HD600, I don't hear any hum (and of course, I don't need the L-Pad).
One question though. My SEX is set up with the 8ohm tap. Would the 4ohm tap work better with these headphones assuming I still want to rotate between them and the HD600 every now and then? I'm not using it anymore to drive speakers.