Re: treble boost/clean boost
The RGW Electronics Bad Bob Booster is excellent and pretty much fits what you described -- a full clean boost with a bit of grit available. It is based on the Jack Orman (AMZ) JFET mini-booster circuit, as are many others (e.g., Fulltone Fat Boost). There are also MOSFET boosters out there, but they apparently tend to sound a bit brighter. The EH LPB-1 is another cool option that is a bit grittier yet than the Bad Bob, but perhaps not quite as smooth overall -- more like a fuller-bodied variant of a treble booster. I think the SD pickup booster may be a spin on the LPB-1 with some added features.
It's best to try before you buy, as they all tend to sound a little different.