Hi M, If a big triode amp is the goal. Consider whether or not a 3-6.5K mid sized transformer would be usable. I know an 845/211 wants about 10K and about 20-30 Watts as well. I have not looked too far into the world of big triode amps, the high voltage scares me too. I have not done enough research to say what tube might work with what transformer.
On the other hand, Ray P of the DC Bottleheads, built a 829 amp that uses a Radio shack 70V line transformer Parafeed. This trans is about the size of an ST-70 chock and it sounds great. go figure.
Go to the Bottlehead forum, search Under Ray P and Meet pics. It’s worth a look.So for the 6ah4 the little Hammond’s might be the way to go. Another possibility, if you have a set of P-P transformers handy from say a EL84 or 6V6 amp, these run about 6-8K. Yea I know a P-P trans is not designed to run single ended and you will saturate the core, at least somewhat. But at very low power it works.
As for the Aikido, I have not done anything new with it. It works POS power supply and all and I have lately been spending my time on my 300B amp, when it is cool enough to run it (92 here in Valley Forge today). there is more over at G.B…John