There are lots of good cables around - have a look at
www.audiodirectory.nl in the section "cables". I'm using the Gotham
GAC-4/1 Starquad cable with double shielding - I think its quite cheap
for what it is (it is really good as far as I know). But I don't think
your problems go away with new cables - better have a look at the
inputs and outputs of your gear; all of them need to be balanced, best
is a hi-quality transformer (Jensen, Lundahl). There are some
tech-papers on this subject, first have a look at the rane-notes
(www.rane.com).

Hope that helps
Samuel