I own and sell Sound Lab electrostats and I've owned Quad 63's and 57's. The requirements for a speaker cable for a full range electrostat are a bit different from the requirements for a conventional speaker.
First, because an electrostat typically has a fairly high impedance in the bass, there is not as much of a premium on high current capability. Second, because an electrostat typicaly has a low impedance at high frequencies, you want to minimize series inductance to preserve all the air and delicacy the stats are capable of. Third, you want a very time-coherent cable, because getting everything spot-on timing-wise gives an almost magical "bloom" to the instruments, as well as a bit better soundstaging. Very few conventional speakers benefit significantly from a time-coherenet cable, but full-range electrostats do.
I have investigated cables for electrostats rather extensively, and the best I have found are Magnan cables, in particular the Signature. Goertz is also good, though I've had customers replace their four grand silver Goertz with the one grand Magnan Signatures after an audition in their own systems. Analysis Plus is good bang-for-the-buck. All of these cables are designed to minimize the "skin effect" and are thus time coherent (the Magnans especially so), and all are low inductance (no twisted wires).
David Magnan uses stacked Original Quads as his reference speakers, so it's no surprise that his cables work well with electrostats.
