Hi Manny,
I've also discussed the same with Jeff Fischel the senior tech / now owner of CJ.
http://www.theaudiobeat.com/news/con..._ownership.htm
I much enjoyed the article for content, as well as putting a face with one of my audio mentors, I wish him the best, I digress.
I have not tried a KT120 as of yet and have not even started the research as to which are favored, You ?
All my CJ tubed amps have factory installed tube sets at this time, ranging from New low hours to Mid life wonderful. GE 6550 s drivers escape me, but can look if curious.
My Audio Research D-250 has been the 6550 consumer with 8 per channel. I love this amplifier but soon realized that if I wanted more affordable output I needed to go SS.
So to attempt to keep the 250 running I bought Tung-Sol JAN-6550 S16 s nos. Years later I have been thinking I had a supply of output tubes for the CJ s. Thinking more efficient.
This all leads to why I wanted to try the CJ ET5 because of it's 1 6922 tube. To try to keep it simple, 1 balanced, quiet, harmonic tube and you are good to go. I Lucked out big time!

Enjoy!
Urban