Hey Dan,
Yes, it was around 93-84 when the Classic came out and the MP-1 was discontinued. The classic replaced the original, but they don't sound the same for the most part.
The Classic has an added voice they called "Brown" tube voicing. There were some other notable differences in the Classic. It also had a built in noise gate, Stereo effects loops, and Direct outputs on the back with a selectable cab emulation.
The Classic retained the ease of editing and storing presets that you had with the original MP-1, but I find the Chorus is much more subtle than the original and the MP-2.
To my ears, the Classic doesn't have as much low end range as the original, but it's overdrives are much smoother and it's very responsive to your pick attack, so you could be in a well overdriven gain setting, but clean it up by softening your pick attack and /or rolling your guitar volume knob back. It's very dynamic and responsive, like a vintage amp should be.
Dante and Gibsonrich are out on the Left Coast, and a few others, we're all over the map!