Audio Research Owners Best 6550, KT 88's Tubes?

With so many tube choices from co.'s like JJ Telsa,Valve Art,Tunsol,Svetlana, to name a few, like to hear from Audio Research owners regarding their current favorites and
why. I'm currently using the Arc 130-SE and EH 6550's but considering KT88's. I realize the Arc is a high current low
voltage amp and that rules some tubes out,but so many choice. After years of using the very linear 6550 winged c's looking for a more "liquoid" midrange.
the best by far are the Original Tungsol 6550,black plates,
then the other 2 grey plates.for kt-88 the Superb golden lions from Genelex. For modern tubes ,
the new Tungsol tubes can handle a minimum 5 more volts on the plate around 43v ,for under 100 for a quad worth a try.