The 6L6 has a distincly different sound from the EL34. So most probably I will just make the amp available with either. I believe that at the end of the day, personal preferences would win. But the El34 is a bit more powerful in cathode bias than the the 6L6. I have not auditioned the amp with a KT66 so at this point I really cannot tell how it sounds. Also infavor of the EL34, it is cheaper than the 6L6. As for the price, I think we are on the target if it is only a basic power amp. I will audition the amp with a 5751 driver tube and also try the 12AT7. If I use the 12AU7 I have to make some changes in the value of the plate reisitor and cathode resistor as 12AU7 is a medium mu twin triode. I will check out which driver tube will sound best. Will keep you updated.