Sony has a discontinued pre that sells used for under $500 (that was the new price I beleive) that was supposed to be perfect for that solution and was rated as stereophile class A.
If you wanted to go cheap, go down to radio shack and get a couple of AV switches. These are the red/white/yellow A/B switches. Since each has 2 channels of 3 switches, you need two. Very slick, very cheap. Don't know how well they pass the audio though.