Yeah, what Zimm said
"RCA" is a termination type, not a cable type.
As a cheap solution, I would suggest using RG59 coax for the cable. If you're handy, you can certainly just use something
like this and terminate it yourself. If you're lazy like me, you can get the pre-terminated coax and screw a couple of
these to the ends.
Like Zimm said, the only issue you might have (which you have probably already discovered with the zone 2) is that many (most?) processors don't like to convert a digital audio signal to analog for use in a separate zone. In practice, this just means that you might have to wire your digital audio sources using BOTH the digital and analog connections to the receiver.
