Know what'd be handy?

[Djinn Guitars]

A tube sub. list or chart. Not just a this'll work in a pinch list. But a this'll work and it'll do this to the sound, and don't sub. this for this or your amp will spontaneously combust.
Have any of you found such a thing? Or would you like to participate in ones construction.

[trevorus]

http://tdsl.duncanamps.com/tubesearch.php

That's worked pretty well for me. You'll have to know a bit about the specs to know if your amp can handle a different type, though.

[Djinn Guitars]

a little of that'd help too.