Speaker wire
Grimis,
It sounds like you already have one stereo pair to the VC and are running the second?
Make sure that you are using CL2 rated in-wall speaker wire for that application such as Belden 5100UP.
One common practice is to run 14 AWG, 4 conductor wire to the VC like Belden 5102UP/EP and run 2 conductor cable to each speaker.