Ok, i'm ready to give my initial impressions of my new PPA/DAC.
Originally I had Sonica (analog) with the black gate mod -> Pimeta -> CD3K. It sounded pretty nice, very clear, but lacked bass extension and impact.
When I use the analog input input into the PPA w/ diamond buffer, I get a tiny increase in sound quality, so small that it could be my imagination. Quite a dissappointment for $300 or so.
When I add the DAC into the equation, the sound tightens up a little, and the bass extension/power improves. It's not a huge improvement, but you can definitely hear it, and it does sound nicer, and better ballanced.
Regarding the whole PPA/Dac/Diamond buffer setup, I consider it poor value for money compared to my earlier setup. It cost around US$650, maybe a little more, and if i'd been able to hear it before I purchased I wouldn't have bothered. I'm considering sell it (and a lot of my other gear) and just getting some Beyers and using them out of a bithead, but I digress.
Remember that this is my subjective opinion. It could be that the sonica's not performing as well as another source might. I bought my DVD player in, but when I plugged the optical out into the DAC there was no sound - it's a cheap DVD player, I guess it doesn't work. There was nothing wrong with the sound before this upgrade either, and the CD3K is very easy to drive, so other cans might get more of an improvement.