6550 or KT88 ?

I had a pair of Premier 12 monos for several years and after a bit of experimenting I concluded they sound best with the GE6550A they originally came with. Barring 2 quads of NOS black plate Tungsols dropping into your lap, my next choice would be the SED ("winged C") 6550C. (Svetlana 6550Cs have the 'S' logo, and are not the same as the SED.)

Rolling the driver tubes in the 12s can have as much impact as swapping the outputs. With the GE6550As, a single RCA triple mica black plate 5751 is a nice improvement over stock and RCA 6FQ7/6CG7 clear-tops also work really nice, or late 50s Sylvania 6CG7 are even nicer.

You might give the "reissued" Tungsol 6550's a try for about $40 a pop. I have heard nothing but good things about both their sound and their reliability.

Just this last year I bought a Music Reference RM-200 tube
amp. The amp came with two sets of KT-88, both RAM lab tested. While they sounded pretty decent, I had a feeling
I could do better. I bought a new quad of Tung Sol reissue
6550's.....OH MY GOD! I am now convinced I am DONE, the 6550's are just that good. It just seems everything is there, be it slam, liquidity, air, you name it. Maybe I just hit in the perfect match for the RM-200, but let me tell you the KT-88's are never going back in; they sounded congested and smeary when compared to the 6550's.
I could NOT be happier.
Your mileage may vary....but luckily I am getting 100mpg.
By the way, a "matched" quad of 6550's was $105!

Atomickid,
I've heard so many good things about the reissue Tungsols that your post may have just pushed me over the top.

Where is the EH KT88 fit in here? My Zeus comes with stock EH,anything better out there?
Thanks
George