Sorry that I'm late to the party, but I do have several thoughts:
a] RG-6 (or RG-59) is a very generic World War II catalog system. All it's indicates is the overall diameter and the Radio Frequency Characteristic Impedance. In fact one manufacture lists over 40 different RG-6 model numbers optimized for all sorts of different parameters.
b] Long RCA analog audio interconnects place special demands on the cable itself. There are several papers and pages on the subject. Here are two from Blue Jeans Cable:
Subwoofer Cables from Blue Jeans Cable
LC-1 Audio Cable Design Notes -- Blue Jeans Cable
c] In summary, a long interconnect requires a very low end to end shield resistancee.
d] Most common RG-6
Quad Shield cables are optimized for very high frequency cable TV channels. This is one of the poorest choices for audio cables.
e] While Cat-5 works well for up to 100 meter long audio interconnects, it's a different interconnect system and can't be used with the typical unbalanced input/output.