So what you mean is not so much that you want to connect 2 screens and keyboards, as that you want 2 people to access the same computer. Does it need simultaneous access? If not then a KVM switch will do the job - assuming that the machines are reasonably close together. But you might find that a decent KVM switch will set you back as much as the upgrade cost for Sage. Another alternative would be to use PcAnywhere or similar remote control software, assuming that the machines are already networked together.