I don't have this head yet but thinking heavily on it based on the answers to this question. I started to do some research on difference in tubes and my head just about exploded. So first things first. -Can I switch the 6l6's in it to 6550's? I heard this might increase the power (Not my intent) and I'm assuming that means more work internally? -Also if there was a 100 watt tube head with 12ax7's and 6550's that is affordable Id jump all over that instead. - Also might switch on of the 12ax7's to a 12au7??? Trying to emulate an old SVT to some extent.