I use a MXR Micro-amp in the loop, it works great. It only boosts the sound level without adding any tonal change. I've been using the same one for over 30 years. I just upgraded all my stomp boxes except that one and my Digitech whammy pedal, so that says a lot about it. I use it in the front end, last pedal, for boost with my 1972 Marshall super lead which I bought when I was 15 in 1978, because it doesn't have a loop. It worked great with that amp whereas everything else changed my tone. But that was way back then, 35 years ago and I'm sure there is other straight boosts being made now, but the ts-9's colored the tone, along with the Boss overdrives of the day, some people swear by those, not me. I don't like the way the micro-amp drives the line when it's first in line, and I don't like it in the front end with any of my Boogies, it works great in the loop though. I had a little extra money after buying the wife and kid's Christmas presents so I got all new cables (Live wire elite) a Bad horsie 2 wah, T-Rex Reptile 2 delay, MXR Zakk Wylde phaser, TC hall of fame reverb, Boss TU-2 tuner, and Mesa 420 6L6's (a gift), =C= EL34's, jan sylvania 12ax7wa's for my Mark IV which I fell back in love with since my band went on a break. I run everything but the micro-amp front end in this order - phase-wah-whammy-delay-reverb. The tuner is connected to the dry out on the whammy. The reverb is a no brainer, I can't imagine using the spring verb that's in the amp, I have 4 distinct sounds I use with the whammy and the T-Rex is like an old tape delay so I'm digging in, so to say.