You can make this switch yourself with a couple of heavy duty DPDT toggle switches, a chassis box, and some speaker jacks, all available from Radio shack.
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But buying it prebuilt from Radio Snack is probably cheaper.
I won't say better. I hd an interconnect A/B box from RS some years ago, and it went bad, injecting amazing amounts of noise into the signal - I thought I had an amp melting down. Never again.
Building your own out of high quality paddle switches (try digikey), 10A or better, is often reasonable. Buying pro speaker switches is generally not worthwhile; for some reason these run for $60 and up, which is pretty much unforgivable.
Don't use the cute little 3A switches, even if they boast silver contacts. 10A is a bare minimum. Bigger is better. Even then, don't switch under high volume conditions - if you cook the switch contacts, you'll start to see meaningful (=bad) amounts of contact resistance and your speakers will sound like low end Bose in-walls.