I wanted to pass this tip along for the Vibro Champ owners.  At Nik's suggestion, I tried this mod and adds a lot of gain to the amp.  Lift the 15k resistor from the volume pot (clip the wire or desolder the connection).  I replaced the pot with a push-pull pot so that I can use the cleaner, low-gain setting with the resistor in place, or pull the pot to the B position to give me higher gain and a lot of nice breakup.

I play my Ceriatone Vibro Champ through one Eminence Copperhead and one Delta Demon speaker in a 210 cabinet.  My Strat never sounded so good...