One fellow that I personally admire as I believe him to be quite forward in thought is Bruno Putzey'sBruno is quite brilliant.
The thing is that cables can cause colorations due to capacitance, interactions with the output impedance of a source, the input impedance of an amp, EMI issues and the like. Plus you can get noise from grounding issues (ground loop) even if a hum isn't evident. In a single-ended connection, the shield is often carrying the signal (in order to complete the circuit).
A lot of that is why the balanced line system was developed- when running balanced (if the balanced line standards are being observed) even though ground loops are present they can't get amplified, the shield of the cable isn't used as part of the audio signal path and so on. So colorations from the interconnect can be vastly reduced.
If your cables are kept short and you are careful with how your sources interact with the passive control and the amplifier, the results can be quite good. But if you are using speakers and are keeping the amps by them so as to minimize colorations from the speaker cables, you might have to run fairly long interconnect cables. If this is the case then the balanced line system is the way to go; you simply won't be easily able to do this with a single-ended connection without coloration.