KT88 tube amp

I haven't heard the KT88 but the Gold Lion KT77 is to me by far the best current EL34 variant. By comparison a Psvane EL34 was unacceptably  bright. Obviously KT88s are different tubes and YMMV.

I recently rolled to JJ's  Natural rich sound - Medium.

I've used ps vane jj tung sol and sovtek, none of which were in a quick silver. Ps vane was the worst performing. Jjs and tung sols were the best.

I use Golden Gate. The quality of bass depends to size of output transformer, quality of power, interstage and cathode shunt caps, dumping factors, and the last - quality of speakers.