1) Hey, it's your money.2) The only reason I can see for $100/foot cables is to impress your date so that you can get her (or him) into the sack. I am a happily married 62-year-old, so I'll spend my money on something else.
3) I strongly suspect (I have the same right to pontificate as the cable manufacturers and the hacks who depend on their advertising revenue) that if you move your sofa six inches to a side, it will have more audible effect than changing from the RS cheapie cables. That is why spending a lot of money on cables is sort of silly.
4) The speaker (including crossover, etc.) is the place where subjectivity, objectivity, and dollars coalesce into the most variable and productive element in terms of final sound. (What if you build a Pi7 out of mdf vs plywood.)
5) Certainly there must be measurable differences between the sound from two different cables, given a sensitive enough instrument and reproduction system. "Can anyone hear the difference?" is another question. I tend to agree that if you think you can, that is good enough. (Wear your copper bracelet and sleep on your magnetic bed if you think it helps your arthritis. I think that glucosamine sufate helps mine.)
If you suffer from painful osteoarthritis and have not tried glucosamine sulfate, you should! You can get it cheap at Sam's or WalMart.