Got a nice deal on an Orange Dark Terror on CL yesterday. Plugged in straight with nothing else I can't say I really care for how these sound, tonally nice but the distortion is too fuzzy and loose for my taste. With an OD808 boost in front and the MXR KFK in the loop, however, it sounds like a totally different amp. Very crisp, very tight, and amazing tone. I love the MXR - pulling down the top EQ slider totally got rid of the fizz and dropping the volume and gain lets me get a really nice sounding distortion at very low volume.
I'm not a big pedal or effects guy but these two are amp-fixers that I would not be able to live without anymore. This might tame my GAS for a Mesa head, for a little while anyway.
I always put MXR eq's in the loop in any amp when playing at bedroom volume. They really liven things up when you can't get the volume.