How much quality do I need in the RCA cable for my receiver to subwoofer (HK AVR-230 to HSU STF-2)? Can I get away with the cheapo $4 15-foot Radio Shack unshielded cable, or do I need to drop $25 on this?

I'm sure this has been discussed, but a brief trawl through the archives didn't find it. If you can send me a link to a past discussion, that would be great.

thanks,
Robert