Forget the KT88's and go with
Electro Harmonix KT90 these are great tubes with plenty of bass at the bottom and have a very strong midrange punch, also they do not grate on your nerves at the top end.I took out my EL34 tubes that came in my PrimaLuna Dialogue Premium HP Integrated and everything just opened up, it now sounds like I wish it did when it came from PrimaLuna.