Upgrade Interconnects for Spectral System

Regarding impedance. These values are given in the equipment specs but a quick call to MIT or Joe Abrams or Spectral should get a quick answer for you. I have also found Goodwin's High End people very knowledgable and helpful regarding Spectral and MIT. I think the EVO 2C3D would be terrific, and no, you don't need matching speaker cables, yours are excellent. 

Joe Abrams may share some thoughts with you. Worth a call.

You are best off with the cables customized for Spectral. Reselling with be slower than with MIT Cables, but if you choose Spectrals best, you won't need to change for a very long time  :)  Mit's customizing for Spectral goes back a very long time, very successful  :)