My experience has echoes Newbee's and Albertporter's. You might consider an amplifier that allows you to use any of these tube types. Then you can switch between them, depending upon your mood. Quicksilver Audio offers this versatility with some of their amps, and no doubt others do as well.
Differences in SQ between EL34, KT-88 & 6550 Tubes
I'm continuing my tube education and am considering buying a tube amp. Is there a distinctive difference in SQ between the EL34, KT-88 & 6550 tubes? Is there a pecking order as your climb the tube ladder for SQ. I am aware that different brands/versions of either tube can sound better than the other. But I was wonderful if one tube type is generally better or has a distinctly different sound than they other.