I was doing some comparisons with the Senns v Denons (AHD-950). The Denon's are a little smoother overall, but the midbass is very bloated in comparison to the Senns, plus the soundstage is very cramped. But they do have a little more impact for rock, so I can tolerate their shortcomings every now and then.

Chrono - do you frequent the head-fi forums? The PPA does look pretty interesting, though I'm not a diy-er. I've got a Gilmore v2, and it keeps me happy (though I'd like to try a tube amp sometime).