There is no straightforward answer to your question about appreciable difference between $6 and $50-$60 IC's. A good quality cable should allow you to hear the best possible sound your upstream components are capable of.
The Kabledirekt cables offers adequate shielding and quality 24k gold plated connectors. If they already sound great then why mess with something that's already great sounding in your system?
I have read comments about your Rega CD player/NAD integrated sounded muddy with your KEF Q speakers in your other thread. Are you trying to fix this issue by switching out to another set of cables?
What brand of speaker cables are you currently using?
From my experience, there is no hard and fast rule about using same brand of cables, but in your case trying out Signal speaker and IC's may offer better synergy between your components.
http://signalcable.com/analogone.html
http://signalcable.com/classicspeaker.html
They are one the best budget cables I have tried in my system. They punch way beyond their suggested 'budget' price and comes with 30 day in-home audition guarantee.
Hope this helps and good luck!