Maybe the Custom Audio Electronics MC-401 Boost pedal that
MXR is building....It seems to be getting alot of good response
from owners in differant applications on the pedalboard........
I have the CAE boost. It did pretty much exactly what I wanted it to do which was boost the input of my amps without changing the EQ curve.It wasnt very expensive. Under $100.
I haven't tried enough "clean" boosts to compare but this one is very usable
the RC booster and full tone Fat boost or Fulldrive 2 are the most transparent i've messed with. The duncan booster is good as well and is cheaper than the boutique stuff. The micro amp works great as a volume boost in the effects loop but what i discovered running it as line signal boost pedal is that it takes some "fatness" from the amp and sort of thins it out.
recently acquired a fulltone ocd, and dont miss my micro amp one bit. takes a bit of tweeking, three knobs instead of one, but once you get the hang of it, it rocks