Been doing this with my Silver Jubilee since the early 90s and still use the same Boss SE-50. If you want to be purist, yes, it does do something to the tone, but all effects do. Get the grit/distortion from the amp, do everything else digitally and it works. I switch patches using a MIDI pedalboard, only downside is a noticeable cut in the output while the SE-50 switches settings, but you learn to hit the pedal a beat ahead when switching. Maybe more modern digital units are better in this respect. Using dual delays in a stereo set-up (doesn't matter too much what the second amp is as long as you can balance levels, but a second valve Marshall is sweet) is a lot of fun, means you can do stuff like Brighton Rock and riff on endlessly with yourself while the rest of the band waits to come back in Another sweet sound is a short delay and a very small pitch-shift/detune on one channel. The guy who suggested that to me worked for Celestion and described the result as 'addictive'. He was right. It's like a chorus but sounds huge through a stereo rig. Worth buying a second amp just to try it. All the reverbs sound great in stereo too.