It appears that you've tried a lot of the best. One I don't see on your list is the VAC Renaissance.
I have no first-hand knowledge of the VAC Ren. pre or many of the other brands you have listed, however, in my limited time with the entry level Aesthetix Calypso, I've learned that tube rolling is everything. The sound quality coming from my Calypso with upgraded tubes is night and day vs. the stock Sovteks. Currently having good success with NOS Mullard CV-4004's.
But I digress... just trying to re-emphasize the importance of tube rolling. It may help get you off the roller coaster of trying more preamps.
I have no first-hand knowledge of the VAC Ren. pre or many of the other brands you have listed, however, in my limited time with the entry level Aesthetix Calypso, I've learned that tube rolling is everything. The sound quality coming from my Calypso with upgraded tubes is night and day vs. the stock Sovteks. Currently having good success with NOS Mullard CV-4004's.
But I digress... just trying to re-emphasize the importance of tube rolling. It may help get you off the roller coaster of trying more preamps.