The BYOC one has all of what you'd want plus what to change to get what sound. You socket the key components and then mess with it. Asym clipping, different diodes (from red LED's to the germanium ones) different resistors for the bass response, the two different chips for the different models, all of it is there to mess with. And some hints, like a brick to the head in subtlety, on how to mod it to get any of the modded versions. If the parts do not come with it, Smallbear has the interesting alternatives. It really is a great kit for the Tube Screamer experiment. Ok, I'll end the advertisement now.
Patrick