I just used my Clip Zip with both of my Audio Technicas earlier.... I forgot that with a little careful EQ tweaks that these are also pretty impressive 'phones. The thing I love about the S500 is no EQ required....in that regard it betters everything else I have, except in soundstage, where the 780s clean house.
So at the moment, I have four headphones I really enjoy, a few others that are decent.....and another set coming in the mail soon. Life is good!
With ATH Pleathers the S500 on FiiO E11 eq2 sounds almost exactly like the same setup with stock pads and eq0. :)