I got into a geeky mood and tried to guess the real-world guitar amplifier (or pedal) behind the amp sims. Just for fun, here's my best guesses:
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Tweed Guy Fender '59 Bassman Tweed (6L6GC, 4x10)
Boutique DC Matchless DC-30 (EL84, 2x12)
US Combo Fender Twin Blackface (6L6GC, 2x12, Super Twin?)
Jazz Combo Roland JC-120 Jazz Chorus (Solid state, 2x12)
US High Gain Mesa Boogie Mark II or Mark III (6L6GC, 1x12)
British Lead Marshall Plexi Super Lead (EL34, 4x12)
British Combo Vox AC30 Top Boost (EL84, 1x12 and 2x12)
British Legend Marshall JCM 800 Lead (EL34, 4x12)
Distomp 1980s Yamaha distortion pedals (SHD-100/MBD-100)
Y-Amp Yamaha DG series guitar amplifiers and stomp
Small Stereo Fender inspired?
Multi FX Inspired by the Yamaha DG Stomp
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Blake wrote an article back in Motif XF days, but I wanted to get down to specifics. More at: http://sandsoftwaresound.net/yamaha-keyboards-which-amp-sim-is-that/

Have fun -- pj