Make sure that the seller used only MIT Spectral cables. It has been told to me that other types of cables will damage the unit. It is also in the Spectral owners manual about the cables to use.
They should only be repaired by Spectral or the warrenty is no good and Spectral will not repair any of their products if someone other than Spectal has worked on them.
It is also Highly recommended that you use the Spectral Pre-Amp to go with the amps, they will not work properly if used with other pre-amps.
I have the Spectral 30SS pre-amp and the DMA-360's mono blocks. I use only MIT Spectral Cables for every hookup.
I'm very happy with the purchase that I made, and Spectral matches very well with my Avalon Radian HC speakers.
Be carefull buying from someone that has not followed Spectral recommendations for cabling.
Give Terry Menacker a call at Overture, he usally has certified used Spectral gear.