Better get something more generic, like the miniDSP. The issue with using MA 1 to align third-party analog monitors with a KH 750 DSP is that you end up with wrong phase response correction, and I don't think you can skip it. I think you can then adjust the filters manually with khtool, but you need to somehow obtain the right values, so it would involve measuring the response with some other tools.
Another option I would consider is to sell the PSI monitors and replace them with all-Neumann setup, i.e. a pair of KH 120 II, a KH 750 DSP, and an MA 1 kit; I think it would be the least bothersome way to achieve a calibrated full-range system.