So, to update a dead thread no one read in the first place, I did get a quad on SED 6550Cs from Upscale Audio, and have them installed/biased. Considering they have some factory burn time, plus some at Upscale, they sound pretty good.
The major difference I am hearing is that the soundstage is a good deal deeper. The stock KT88s pushed the mids forward, which I suspect would be a very smart choice for many bookshelf speakers.
TJ Full Music pre-amp tubes are on the way, along with some Herbies tube dampers. Fingers crossed this will be a winning combination, as I am out of cash for a while.