The string does take more abuse than the cable(s) so here's what I'd do. I'd order a complete set + one extra string. Next time you need a change just change the string. The cables should still be good unless you damage it/them in some manner.

As for brands? Personal matter. I have used Winner's Choice and they are good, but I've also used Prostrings, Backnasty, and recently H&M and find them every bit as good as Winner's Choice, but at a lot less money.

Not that a few bucks means a lot, but shooting a Nitrous X system calls for a string and four cables so it's a lot more than $25 difference.