Now back in the day 99.9% of the LA Hair and Glam scene was pairing their 2203/JCM800 with some OD or Dist pedal or other to get a more focused and higher gain.
The (original) MP-1 took that and transformed this refined (pre-)amp sound in a preamp circuitry, add MIDI, one Solid State and 2 Tube/IC channels, an FX Loop and a Chorus.
In my book the MP-1 is "The" hot-rodded JCM800 of the late 80s/early 90s.
Now the 3TM takes that initial vibe and moves it one step (or better 2 Triodes
) further. If I were tempted to give a comparison: Marshall 2555 Silver Jubilee on maximum steroids
If you wanna go a tad bit more to the traditional Marshall sound/vibe I´d say Mod1 (cathode follower).
For a more modern (think DSL/TSL/sorta JVM) Marshall sound the Mod4MkII does the trick.
That leaves Mod3.1 and 3.666 ....
Question: What do SLO100, 5150 (block letter) and DualRec have in common??
Answer: The overall preamp circuitry design (by Mike Soldano = SLO100)...just some alterations in terms of gain stages/cascading here and there....don´t forget the Recto poweramp design....
Strip them all of their poweramp stage and back down to their bare simple preamp and the blueprints are not that different from each other.
YMMV.....