I've been reading about the Ampeg V4B and it seems like a lot of players love the sound but eventually need more volume, so some of them have the amps modified to accept more powerful output tubes. Is this common? Is it more expensive than upgrading from a v4b to an full-bore SVT? It sounds like a good option for me. I'm not quite sure if I'll ever need more than 100 watts of volume ever again, but it'd be nice to know I could get it changed to a 200watter if I needed to. Plus, I've been finding more and more deals to get v4b's rather cheap.