Which tubes are the best?


Hi folks, I just got a Muzishare X7 integrated amp. It is beautifully made and sounds like it has a lot of promise. Even though I'm just breaking it in, I am thinking about tube changes. Why? It's just what I do. 
I'd like your opinion on the best replacement tubes, meaning smoothest, most "tubby" and mellow tubes. 
I won't be chasing NOS tubes. I'd like your experience with Gelenlex Gold Lion, TungSol, Mullard, Telefunken, or?,  etc. of current manufacture. The amp uses KT88, 12ax7, 12au7 and CR34 rectifier. 
Any thoughts about KT88 vs 6550 would be appreciated. I used to prefer 6550 way back when. 
Any information would be appreciated. Yes, I could go through all the old posts but I do have vision issues after four operations and that's why I'm asking straight out. 
Thanks in Advance. 
Back in the day, I used to do some serious tube rolling. The absolute mellowest, most laid back and detail rich tubes I ever found were some Mullards advertised in the back of Audio magazine. They had Magnus Organ printed on them. They were amazing. Unequalled. Ten years ago, I was cleaning out stuff and took a box of my small tubes to a local dealer. Some guy gave me $350 for them. Wish I still had them heh. 

fredcdobbs
The Psvane KT88 supposed to be very good, but I’ve heard the Gold Lion are the best KT88’s.  The best 12ax7 is a 5751, that’s why cj always specs them in their preamps.
Thanks Lou. I have worked hard to put together a nice solid state system but now That Old Tube Majic has me in it's spell. 
Years ago I tried all kinds of tube stuff. Musical Reference, Cary etc. Nice to be back. I never got the point of having tube gear that sounds like SS. 
as i understand it this muzishare unit is basically a primaluna knockoff with a tube rectifier and downgraded output transformers

so i will share my thoughts on tubey tubes

old stock ge 12au7/ax7

tungsol (new russian) 7581’s if like the primaluna’s this unit can autobias and run 6l6gc/kt66 equivalents - in general i find current russian power tubes less sharp and treble intensive than the chinese counterparts
You can't go wrong with any of the Slovakian-made JJ's! I'd replace the Chinese tubes presently in your amp with all JJ's!