smart relay

You could wire the switch to the clock input of a flip flop.  and then on the compliment side of the flip flop wire that to an n channel transistor and use that to drive a relay.  You wouldnt need two relays, you could use the normally open/closed contacts.

Unless you want relay 1 to turn on when you turn the switch on, turn the switch off and relay 1 turns off.  hit the switch againa and relay 2 turns on turn it off and relay 2 turns off...  If that is what you want then you will need a bit more.

Here's what I've done in the past which will work for you using good 'ol relays:

I see you need a Display controller for picking which stereo to play. With this circuit you can go up to 10 Relays Only a few are shown to make the circuit easy to follow. The other relays need the same patern repeated.

I have a programmable relay controller you could do this with. ill-logix.com