There are advantages to biwiring speakers. But the speakers and the electronics must be capable of this.
Bi amping is another technique for improving performance. But again, as above.....
There are numerous good to excellent quality speaker cables to fit all budgets. Prices can range from less than a dollar a metre to several thousand per metre. No doubt you need to look for a heavy guage (lower guage number, heavier the wire) 10 or 12. Also purchase good quality connectors for both the eletronics end and the speaker end. Monster Cable is a fairly common and readily available brand. I would start there, and look upward if your budget allows.