what is the best Kt88 to get

Verbosity is good as hand signals or morse code rarely gets the point across around here. In recent years I tried (mostly in a factory modded Jolida 502P I recently sold...great amp) new version Tung Sol 6550s that were certainly clean, along with Sovtek KT88s (no longer made), and various others like Gold Lion KT88s, KT120s and 150s. When I bought a small SEP Dennis Had amp it came with Gold Lion 88s which are great, and the Sovteks also sound killer in this amp, but I returned to a fave, the KT120s, as somehow they work for me...plus my last quad was used enough to wear 'em out over a couple of years, so I guess I like the sound.

I replaced my stock McIntosh tubes with Psvane Black Bottles KT88s in my MC275 and was a noticeable improvement. This was 4.5 years ago and still sounding great.

FWIW I purchased 5 in case one failed, on rotate then every 2 months so they all age similarly. No failures.

What amp do you have? KT88s can sound different depending on the amps design.  I found Gold Lion KT88 to sound very good in my Primaluna Dialogue Premium versus other KT88s. The worst was Preferred Series from the Tube Store.  This doesn't mean they sound bad in another amp so I'm not trashing the tube.  It just had too much detail and energy for me. 

I had a pair of "preferred series" 7025s that didn't sound as good as Gold Lion 12AX7s in my hifi rig, but work fine in a guitar amp. Who knew? I'm happy to share this revelation with others, as hey...I'm a giver.

What amp do you have? KT88s can sound different depending on the amps design. I found Gold Lion KT88 to sound very good in my Primaluna Dialogue Premium versus other KT88s. The worst was Preferred Series from the Tube Store. This doesn’t mean they sound bad in another amp so I’m not trashing the tube. It just had too much detail and energy for me.

My experience is precisely the opposite in my VAC 300.1a. Just goes to show how much the amp affects the performance of a tube.