Yes, I have 6 or so various op-amps that I ordered based on your op-amp page. When I started building this amp I sat down with my little Cmoy and did some testing. the Cmoy is easy to roll op-amps in, and its just the op-amps in the circuit so it makes for good A-B comparisons.I really liked the 823, to me it really expanded the "sound stage" and "depth" compared to the others i had (sorry, don't have them in front of me so i cant give the PN's). All the others sounded kind of flat by comparison. Plus the 823 just sounds lively or fun if you will. I actually preferred the lowly little Cmoy with the 823 over my mini3 (the HP build). I did find that it did not have the grunt my mini3 has, but i did prefer the sound. As you say though with the buffers its a non issue. In the Pimeta running 12 volts, even with the standard gain (4.75 R4 if memory serves me, gain of ~5) its plenty loud!.
Tangent, just got the parts I ordered from you last week, so i can finish this one up. Thanks.