At the moment I am contemplating adding the Usagi preamp stage into the chassis of the Yokimbo output stage to save some desk space by having one preamp chassis and one or two power supply chassis less as they could be integrated with one another. A high Dunker factor is nice and all, but not really wieldy or pratical.
Sharing the supplies will also allow me to play with tube positions a little regarding preamp and driver sections. I want to try out the 4P1L and reading all the rave reviews, it will end up in my amps after I check it out myself. This might be a good combination to build as little yet try as much as I can :) I'z lazy!
The 26 and 4P1L will share the same 170V supply, and the 801A (or 10Y if that stays as a driver) will share a 500V supply. Filament supplies would all fit in the same chassis as well; 6x 18V/3A raw DC with six Coleman regulators in the signal chassis. This will save me two sets of connectors and cables to bring the raw DC to the signal sections.
The 4P1L has a much lower plate resistance vs the 10Y, so it could act as a full-range driver with the same 1:1 interstag which has 50H induction. It was meant to roll off below 75Hz when using the 10Y as the output will only feed 150Hz or up as the bass is handled by another amp/speaker.
Another advantage of the 4P1L is that is has more juice to drive the grid of the 801A positive into A2. As-is with the 2:1 on the 26, I will have just enough gain to go a little positive on the 801A grid, but I could always switch the 26 to a 1:1 output and swing around 180-190Vpp into the 801A. I think this will melt my speakers though, so...