I have the Catalinbread Super Chili Picoso. It has 35db of boost available, and its a clean boost. He also produces a Sogrando Picoso (?) that has an increased midrange boost. Either way, 35db is a lot of boost. It works fine for me, but I only ever used it on my Line 6...(there are samples in the players bit). I, for some reason, haven't used it with my JCM800 - I don't have an attenuator at the moment so I don't like the overdriven sound of the amp at room level, so for my distortions right now I mostly use a fuzz. I reckon though, with a properly overdriven amp, it would sound wicked. I'm getting my hands on an attenuator tomorrow hopefully, I should be able to report back!
Most boutique guys make boost pedals, basically cos I think they are a very simple circuit!
Some names to search for:
Cusack, Keeley, Monkey FX, Dytone, Build Your Own Clone, Retroman, Aramat, HBE, Fulltone, Kaden, ZVex, D*A*M.
There are loads though, including the MXR Micro Amp. The different boosters will have different tonal qualities and different amounts of boost, and therefore power. It's quite an organic effect, and you might find something you like, you might not. You can boost with a standard overdrive pedal too, though, by increasing the 'level' button. Of course, thats probably not a standard boost and maybe won't be so good at it...Also, some overdrives now come with built in, independent, boost circuits. Lots of choice!