I have done a few relic jobs on my stuff. I think it's cool to have one or two around. I personally don't relic a guitar thats in good shape nor expensive guitars. I snagged an '89 Fender MIJ Strat for $500 that needed love so I relic'd it.
It's a careful and slow process for me but I like it...
Honestly preamp tubes change more for me than power tubes. I rarely feel a substantial difference with any tube swap. The subtleties are there.
The few times I have noticed a major difference was when changing from say a 12AX7 to a 12AT7 or changing powtube type.
One MASSIVE difference was...
I just bought some 5881 and EL84 Soviet tubes for dirt cheap on eBay and I like them.
Is there a cheap Russian 6V6 equivalent that I can nab up cheap?
I would be buying 20+ to stock up if I can find one.
I would say to open the chassis and inspect the SGR, if it's good swap tubes and bias up. I say that in order. Because you need to open up the chassis to bias anyway and if the SGR is the culprit it would take the tube.
Honestly if that doesn't do it, call Scott. Super cool guy and ALWAYS...