I'm not familiar working with the SPM, but I bought some bare Quattro Fil here and found it to be a straightforward cable to terminate. The ribbon construction of the SPM may make it more difficult, but since the cable is already terminated you may be able to take it apart, desolder, and then resolder to your new plugs taking care to maintain proper orientation.
I'd be more than happy to take a look at them for you if you'll spring for airfare! :)
I'd be more than happy to take a look at them for you if you'll spring for airfare! :)