What tube to use in Sonic Frontier Power 3

I know the stock Svetlana 6550C is flat sounding, I have listened to them long enough to know that. I have heard Sovet KT-88 is on the brighter side and not as refined, Svetlana KT-88 is the better choice while Tesla KT-88 is even better if reliability is not my first priority. Kevin at Upscale Audio mentioned in one of the thread Ei KT-90 sounds better than anything above but does not work well in big amps like Power 3.

Then there are Electro-Harmonix 6550 and KT-88 (just came out), but reviews on EH6550 is mixed and I would like people's feedback before I commit 16 tubes.

Also, what driver tubes work well in SF Power 3? I do have 6H23 in my Line 3 buffers, so I am thinking of using 6H23 for Power 3 as well. Is that wise or I will get better bang for the buck by using better driver tubes and ok output tubes?

Thanks for your input
you might try just changing the drivers lst. i use svetlana 6550c's. i had sovtek 6922's which i traded out for tesla e88cc's. the tesla's are not as cold sounding as the 6922's. by the way i have the 6h23's in my pre amp - not that much difference between them and the sovtek 6922 (nos sovteks that is - the new sovteks define cold!). in my application i found the svetlana kt88s to be very clean in the highs/mid range but i found the bass a little lightweight. have fun!
Thanks Newbee. I forgot to mention I like fuller and quicker sound, bass is not as critical to me as long as it sounds realistic. My rest of equipment is SF Line 3 SE, Sony SACD, VPI TNT, BAT VK-P5, and SF Amati Homage.