Thanks Sean ... I think that there's merit in the ideas in your post, and the ideas in my post. I guess my previous post suggested that noise FROM the transport was the dominant effect, and that's a bit too sweeping. However I have an old transport that actually interferes with my TV if I have it plugged in on the same circuit. Putting a couple of ferrite rings around the (very cheap, stock) power cord reduced the interference, leading me to try discover that it also improved the sound of the hifi (which initially surprised me).
I have to admit though that this is an ancient transport and it's quite possible that some of the large electrolytics in the power supply are not very healthy and contribute to noise being modulated onto the supply lines. If I didn't have an 18month old sapping all my time and energy then I might swap them out and see what difference it makes.
I like your point about cables being a patch for a poor component ... I entirely agree.