It all depends how deep down the rabbit hole you want to go. If you're considering inserting an audiophile switch, where currently a switch isn't actually needed, I'd say you'd have to replace the CAT 5 cables with audiophile CAT 5 cables for the synergy it may provide. You wouldn't want any improvement from the switch limited by inferior cables...
No one will be able to give you an absolute answer. I would think that any answer will probably be laced with unproven pseudoscience (like my answer).
Bottom line is whatever helps you sleep at night...