Help!I'maRock!
Mediocringly Derivative
http://www.effectsdatabase.com/model/maxon/808/od801#pictures
I've been looking for a Big Muff. I tried the Green Russian and hated it. In reading about Muffs, I thought about what I wanted. Gobs of distortion, obviously. But I wanted it to play well with my Fender based Allen Encore too. My next choices were either the EHX Op-Amp RI, or a Ram's Head clone.
Deep in the bowels of @Kit Rae's site, is some info on the Maxon D&S and Ibanez OD850. You might consider the Maxon (and it's re-branded Ibanez brethren) the first boutique tweak of the Big Muff. Maxon changed the range of the tone control, focusing it in the middle range of what you would find on a stock Big Muff. And then of course they put it into a much smaller box.
Now I'm not sure about lower noise transistors and all that. What I can tell you is the 10" speakers in my amp don't sound like they're going to jump out of the cabinet due to the massive bass (like with the Green Russian). It has gobs of distortion, as you would expect. It's close enough for my bad Gilmourish wanking. And it plays well with humbuckers. Seems like it's the one for me.