Best 6550 NOS Power Tube for CJ Premier 11a?

If price were no object...and the only goals were tone and longevity:

GE 6550A ?
Tung-Sol 6550?
Sylvania 6550 A?

new production 6550 kt88 very very good now... not sure NOS is the ticket unless you like to burn extra money

check out kevin deal or jim mcshane sites

to offer more exacting advice, i would need to know your intended amp, speakers and what you are looking for sound wise
The folks who rave about NOS power tubes have amps with maybe four power tubes in them.  Many of us who have a large numbers of power tubes per channel have learned to live with the new production longevity issues. That's why I only buy power tubes from the two gentlemen listed in the previous reply. 
I’ve purchased numerous octets of both the Sylvania and GE 6550’s, over the last few decades, from both Upscale and TC Tubes.      Both brands gave me the dynamics, spaciousness and clarity desired.      The GEs were slightly ballsier in the bottom octaves.      Tried some Winged ’C’ from Svetlana, before the plant burned (years back), which were nice.       If still available, I may have gone back to them.      Since I’m now on a fixed income and they’ve gone up in price(if/when they can be found); I compared my last set of GEs (still meter testing half-way into, "GOOD") with a new quad of Russian, Gold Lion KT-88, re-pops.      Four KT-88s in one Cary monoblock, four GEs in the other.      The KT-88s were as nice in every aspect, but- slightly lacking on the bottom, far as punch.      Listening; I use SS amplification, below 80 Hz (actively/steeply crossed), so- that’s not an issue.          When testing/comparing tubes; I run the mains full range, of course.      TC Tubes and Brent Jessee are currently my go-to-guys, for power tubes.
I'm looking for extended bass, magic midrange, delightful realistic and not overly etched treble and extraordinary lifespan and reliability...just a few things  ;)
there are now modern russian and chinese 6550/kt88 variants that deliver substantially more power and better bass response that old school/old design ones - kt90/kt120/kt150

using these tubes has been the whole model progression strategy for audio research tube amps for the last 10-15 years (since the vt series amps) -- objective being to deliver more clarity more solid and controlled bass more linearity, all the while preserving the 'tube magic' higher in the freq spectrum, so to speak

problem is not all amps can run with the higher bias currents and run these tubes properly 

so in your case you shd call jeff fischel at cj - ask him specifically if the prem 11a can handle higher power rated tube equivalents mentioned above... i suspect it may not, given its age

btw, the cj tube amps were quite musical sounding but definitely wimpy in the bass department... that’s why some 20 years ago i sold my prem 11a xs, went to arc, and never looked back - just one data point for you...
I think I would explore old stock options for driver tubes, etc. I usually find they have a greater impact than the power tubes. 
I have both NOS and re-issue tungsol 6550s, splitting hairs but pretty close.

also the chinese offer some really great sounding tubes. Used to have a premier 11a. If memory serves ran KT90s in it.

check out the PSVANE gray glass KT88s. pretty nice tube.
Can we refocus:

Want ti replace the Power Tubes in my CJ Premier 11a with NOS 6550. Don't want KT88, KT 90 or any other tube type. NOS 6550 only.
I am told the amp was originally voiced with GE 6550a. I have located those as well as various NOS Tung-Sol. Goals are more bass but "tuneful", NOT "Thump, thump", extended frequency but NOT fatiguing or over etched, and "magic midrange, more like EL 34, with longevity and reliability. I am presently using   Russian "Tung-sol 6550."
I'm ultimately going to replace the signal tubes as well:
V1 and v2 are 5751
V3 and v4 are 6FQ7.
Suggestions please from those who have actually heard tubes in this amp...and remember please don't suggest substituting a tube type.
Also any experience with:

Vintage Tube Srevices
HiFi Town


I cannot speak to the tubes you are seeking; but have dealt with Early at HiFi Town and have found him to be extremely helpful.  His emails are full of useful information.  A true straight shooter.

Have fun!