One other avenue that you might be interested in checking, instead of buying another Rotophase, is to get a variable frequency AC drive. Typically, if you buy a unit that has twice the desired motor load capacity, you can feed single phase in and get three phase out. Example: buy a 10 hp AC drive to run a 5 hp three phase motor.
If you think you might have use for variable speed on the motor you are planning to drive, this might be something to think about.
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)