Hello Peter - I think you run a real risk using cables other than MIT with those amps (which I think are among the best in the world:)). I use Spectral amps as well (360 at present, DMA 260 coming next week) and have been discussing cables over on the Spectral forum, there has been some good input. I'm currently using Oracle MA-X and find them to be an amazing tool. I have used the MIT/Spectral cables then moved to the Matrix 50 and now the MA-X. With the MA-X you get tremendous authority, presence and depth and all this comes while maintaining tonal accuracy. The improvement is substantial...very substantial. It's hard to articulate everything that they do so I will just say I recommend giving them a go. I think you would likely get a similar impact from the Oracle MA and even more from the MA-X revision 2. As for speaker cables, I am using the Matrix 90 HD and sort of stuck there due to cost. I can only imagine what the addition of the MA-X speaker cables would be like.
Be really careful using those other cables, you can fry your amps pretty quick.