Good question - that's basically the setup that I'm going for as well. (except I have a 28")

All I can think of would be some sort of hardware switch. Whether you do it through a KVM or maybe just run splitters and hook up each monitor to each PC. If you do that and then if you monitor has some sort of keystroke to swtich input streams it could work - but still seems clunky at best.

If anyone comes up with something better, I'd be interested.