Hi Nvp - apologies for the late reply. Yes the upgrade bug has bitten and yes I have listened to the A-46 versus the P-6100 and preferred the A-46 which I thought was a lot more musical, especially with the ribbons on my K6s. I considered the A-65 but it doesn't have two speaker outputs, which is what I need. So it'll be the A-46 for me.
As for preamps - no, I haven't listened to any yet. I figured I'd add the A-46 first, then wait a while (and save like mad!).
Dfwmediagroup - thanks very much for your input. Yes, I think if I do decide on a dedicated preamp, I should seriously consider the C-3800. Will have to see how the finances go after the A-46 purchase, and also whether I can have a home demo of the 2820 against the 3800 to see how each performs in my system.
Many thanks again for your inputs guys.