I suggest that if your goal is to link the Mopho keyboard to a Tetra to get close to a Prophet 5, you might consider this:
Prophet '08
The '08 is about the same width as a Nord Lead, you can control it all real time from the panel (Tetra really requires software), 5 octaves and no wasted space at the ends, Killer sound (watch the demos), 8 voices, and the price difference is negligible.
You don't need software for the Tetra if you hook it up to a mopho keyboard... Also, the prophet doesn't have the suboscillators and feedback functions that the mopho and tetra have. Makes a big difference in sound.