Acutally, the Vox VR30 (as well as
the VR15 and all of the Vox Valvetronix stuff), the tube is in the power amp section. There's plenty of info out on the web on the way these Valve Reactor amps work.
I just got a VR30 a couple of weeks ago, and I'm quite impressed. You might not be able to play a stadum with it, but I'd be willing to bet that in most clubs, you could get away with it with no issues.
Here's a thread on the Vox VR series from The Fender Forum.