I got to spend a lot of time with a fellow rig-talker's Chupa and man, what a beast of an amp! Serious value. I can't imagine a modded Marshall type amp getting much better as far as the base tone goes. The loop wasn't stellar but it was still usable and that amp could do everything from plexi to crunch to modern metal.
Buying from here may cut down on shipping, no?
http://ceriatoneusa.com/