"Any amp that uses 6SL7's should take the 12SL7's. It is virtually the same tube but can handle roughly twice the voltage.
"
Wrong, don't be stupid. It's got a 12v filament, not 6v. It's not going to plug in and work in anything designed for 6SL7s.
Now, change the filament voltage to 12.6v and it will work, but that's more complex a mod than many people are ready for.
And the ratings are the same as 6SL7, nothing is doubled except the filament voltage requriement.
Man, you'd hope people would actually know what they were talking about before they start running off at the mouth. (or the keyboard)
BTW, nothing commercially made is going to be set up for 12SL7, since it's not a tube currently in production. There are a few custom builders who will/do use it though.
-Ed