Hi Classact, it looks like the upgrade and Accuphase bugs have bitten you well, viz. less than a year ago you were contemplating whether to buy an Accuphase or a Musical Fidelity integrated, and now you are thinking to go after the Accuphase top of the line pre-aplifier.
While I do not have experience with either pre-amp, I advise you to proceed with care and patience. I know you have ProAc Response K6 speakers and you were planing to buy an Accuphase A-46 power amp. IMO none of the two is no where near the league of the C-3800 pre-amp. Consequently, the price difference between the C-2820 and C-3800 might be better spent in another direction, e.g. buy an A-65 instead of an A-46, or use it to partially cove the price of a good Accuphase digital source. I would also not dismiss just yet the Accuphase solid state power amps, e.g. the P-6100, P-7100 or the evolution of P-7100 (which should be release in the very near future).
Given the amounts involved I would not take a decision before doing the following comparisons:
1) A-46 & C-2420 vs. A-46 & C-2820
2) A-46 & C-2820 vs. A-65 & C-2820
3) A-65 & C-2820 vs. A-65 & C-3800
Oce you have settled on a pre-amp also compare the A-46, A-65 and P-6100 power amps. (Of course, you should use your speakers when make any of these test.)
Dfwmediagroup, maybe you could shad some more light on the differences between the power amps I have mentioned above. You seems to be a deal so probably you have much more experience with these amps than me.
Good luck and keep us posted.
Paul