what is the best Kt88 to get

In my Ayon Spirit 2 I found the Shuguang Black Treasure KT88s to provide a fuller more pronounced sound than JJ's or even the Gold Lion's . 

Yes, output tubes will also affect your system’s sound/presentation. My previous octet of output tubes(in Cary monoblocks), were 1970’s, GE 6550As. Two sets of the same and a couple octets of Sylvania 6550s, before those(all mentioned being NOS, at purchase). Both of those were chosen, for their very clean, extended, uncolored sound, and wide, deep staging(like your Sylvania 6SN7s). One of the last eight shorted, after a few years of faithful service(50% of GOOD left, on a Hickok tester). Given the prices/scarcity of NOS 6550/KT88 types, I looked for alternatives. TC Tubes found a close match, for the GE 6550s, in their, "too weak to sell as new" NOS pile and gave it to me. Mean time: I bought a quad of the Russian KT88s, made by New Sensor and labeled as Genelex. With a quad of each installed, and my source in mono, I compared my amps. After a few hours, they were very close in presentation, with the(half life) GEs still having a slight edge in bottom end definition and dynamics. I have an actively biamped(bypassed during listening tests) bass system, so- no issue(for me). Now I’ve got an octet of the Russian KT88s and my ears are happy, once again. They’re pretty too! https://tctubes.com/images/view.aspx?productId=1463 The, "BEST" new production tube, would be the EAT KT88 though (to be honest), IF you’ve got the juice. https://www.tubedepot.com/products/eat-kt88-diamond-power-vacuum-tube-matched-quad Sorry for the verbosity!

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.