Im not sure but i think i KVM switch will enable you to use 1 monitor and keyboard on both comps, but i aint sure how you are going to enable multiple displays from both comps maybe a KVM will allow you to that too
I have a KVM from Starview (SV421DD) that does what you are asking. Big problem with it, though, is that you are forced to use a PS/2 keyboard and mouse. There is probably a product from that which supports USB.