I don't quite understand, how you can be down to about 4 preamps, hence you (seem) to know little about it. I presume you have read the sales-blur?
I have had the Accuphase E550, regret having sold it. This integrated is somewhat a C2400 plus A30, and it sounded just splendid in a cool unassuming way.
And thats where I try and answer your question:
There are some really good second hand units to be found:
BOW the Warlock
ML 380S
both these units have a slight dark background, but are very transparent.
Tubes:
Berning the new ZOTL preamp I have it, love it, phenomenal phono stage!!! (Very comparable to the Accuphase, but somehow seemed more charakteristic, fast?)
Solid State:
Audiopax M5 Great but you might end up changing your settings more often than you'd want. Again, this could stand up to the Accuphase when properly set up!
Am afraid, that was not very useful?!