Hey Benny,
I don't have recommendations on all your questions. I'm sure Hugh and others will. But, I have two comments:
1. The Cardas RCA's have a brass base. If you're willing to pay $17.50, I would recommend paying $20.00 and get a pair of Vampires that is solid copper with a direct gold plate.
2. Although you will get more noise cancellation with such a high twist rate (16 turns/inch), I have heard that the sound can get harsher if you do this in signal wires. I don't know what an optimal twist rate is for signal wires. I used 6 or so.
Good luck,
Steve