Well, cable impedance does not matter until the cable get to about a quarter of a wave length long in length. For audio frequencies thats about 2 miles.
For what I can gather about their designs, they should have very high capacitance. This is because you have the braided copper shield-like (essentially) signal conductor, and a very similar shield in close proximity. If the cables have a seperate ground conductor, it could get much worse. Ironically, high capicitance can roll off the high frequencies they are trying most desperately to preserve.
Having said that, I would still buy their cables over most other brands.
EDIT: They have a new top-of-the-line gold plated copper litz wire interconnect out now. The early level model looks like the best of there line, because it has the fewest conductors.