From experience I think the cable can make a difference, but I don't think you have to spend a fortune. When re-doing my cinema room at a new house I used Chord Carnival Classic, and I feel it made an improvement to the sound, (richer mid range most noticeably), compared to the previous Phylex 72 strand OFC I had used. I believe both of these were the same gauge. But the Phylex stuff was still good and I ran it for a long time with no worries.
It is a new room obviously, so this could have an effect but I think it's actually less ideal acoustically than my previous one.
The sound is an electrical signal so obviously what it travels through can make a difference and diminish or alter the electrical wave. Gauge, number of strands, and material, (OFC copper as a minimum), are key as they affect the resistance of the wire to the signal, but the way the cable is put together and shielded could also have an effect, (having said that mine is not electrically shielded, but has a thicker and better outer then the Phylex did, which will help, and the rears run with power wires at some places and the sound is still great). There's also robustness when running through walls and stuff to consider.
My advice would be to check the gauge, (there are tables for length I believe I made sure I got 14 which I think covers you for most normal runs), and then get a reputable cable at that gauge that is OFC at least, (silver lowers the resistance a bit more but I'm not sure it's significant), and a robust outer. Some of the exotic cables i think have more theoretical than real benefits, but I still think you need decent cable.