Vortex Sound Research

So I have a Roland System-1. I like it. But what if I wanted to buy another 2 octave synth that is as different from the Roland System-1 as possible? My goal would be to buy another 2 octave synth that has the most features that the System-1 does not, so that I can add as many capabilities and sounds as possible. Keyboard must be full size. Synth must have its own keyboard (or, Boutique line, I can buy a K-25M) so that I could in theory play them separately.