I have used a bunch of stuff - Boss GE-7 ( I have a BCB-6 pedal tray that was my first pedal board and just won't die), MXR Micro amp (does exactly what it says on the tin), SD Pickup Booster (like the Micro amp but with a little tone shaping, mine seemed to have very low noise, which was good). Mainly using the LegendarY tones Time Machine Boost now - expensive, yes. I bought mine used and it was still expensive. BUT I think the mix of the germanium rangemaster style boost with the blend and switchable cap to revoice and the ultraclean-more-clean-gain-than-you-can-shake-a-really-big-stick-at sides is super useful for me, blending it with various overdrives/distortions/fuzzes (the booster goes last) and also using it to batter my amp input, depending on the gig/tune/how I'm feeling at the moment.
I tend to always run my booster after all the drives etc and use it so I can always extract a gooodly volume jump for solos etc, some others here use them before their drive to make their ts-9's work harder etc....as always, YMMV.