If the cost doesn't scare you off, the SED winged C (=C=) tubes are great. I replaced the Mesa STR440 chinese tubes in my Electra Dyne and am very happy.
I play mostly Blues and Rock.
You can expect crytal clear tone from the =C= tubes. The harmonics are great. On the gain side, they are less gritty with better definition and carry your guitars tone better.
There are also plenty of other great tubes to choose from, but the =C= seem to get the most votes around here.
For your preamp a Tung sol 12ax7 RI in V1 should also be a good improvement.
