Upgrade Interconnects for Spectral System

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  :)

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

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.