Sure, I'll definitely try and make some comments. A bit difficult without being able to make any direct comparisons, but I have a very vivid recollection of the HD600s (wow), so that should help. I'm not expecting a similar level of transparency (or indeed tonality/character) from the 595s but ballpark will be fine.
I'm quite intrigued by the effect of the angled drivers. I've read several comments in reference to other similar designs pertaining to the more natural soundstage this is supposed to produce.
Source is an M-Audio Revo soundcard, either direct or through a NAD C350 headphone output - not sure yet, although the latter is far more practical. Not ideal (and I'm not exactly sure how the NAD handles headphone out in "power amp" mode, as it is) but I'm a student so am well into my overdraft and can't afford a dedicated headphone amp just yet.
Actually... part of the attraction of the HD595 is the lower nominal Z vs. the HD580/600. Should be less demanding in terms of amplification.