I have been tempted to try out the very same dac but they get snatched up on Audiogon so quick and they are always well over $1k.I hear good things about it though.
Speaking of "nicking" if a PS1 ever gets a ding in it Grado will not replace it with a newer one as they are all out of those parts.Don't ask me how i know.
It's the same guy selling them on craigslist and has a couple pair of HP-2's as well.I would pick them up if i had the cash.
http://sfbay.craigslist.org/eby/ele/874738702.html
I owned one for quite some time and i preferred it over my MPX3 SE but there was something about that PPX3 with 5687's which was just go great with grados.Out of all the amps i have let go that is the only one i regret selling.On the bad side the amp would get very hot so an upgraded xformer is a must upgrade.