The ultimate integrated amp.

Interesting addition to the mix, the MBL.
http://www.stereotimes.com/amp051905.shtm
(It was a slow loader for me.)

Might as well throw in the Mark Levenson 383.

Holy moley batman, I just was at Audio Review checking out what the consumer thought of the 383. I was shocked.

I've been doing some similar exploring... what about the Plinius 9200? The fact that it has what appears to be a pretty good phono section is important to me.

If you want tube then you should listen to Audiomat Recital.

If you like SS then the Nagra MPA (yes there is an integrated version available) should be at the top of your list.

Both are quite expensive but you asked for the best.

What is ultimate to one may not be to someone else and "ultimate" to me means price no object; I suspect there are some extravagant integrated amps I haven't heard of.

All that said, if cost doesn't matter I'd like to have a VAC Phi Beta if for nothing more than to stare at!

At more reasonable prices, Hbarrel gave a nice list and I'll add to that the Musical Fidelity kW500, I am biased though, that is what I use; consider Audio Note as well.