Hardware Advice for Single CPU Multi-User Setup


I need advice/suggestions for a system unit hardware(preferably, prebuilt). We want to setup the system unit to serve 4 architects simultaneously. We will connect multiple monitors, mouse, keyboards, usb hubs to the 1 system to serve all 4 concurrently, but independently. This way, most of our our investment will go into hardware and not software, as against getting exclusive systems with software for each of the users.
If anyone has experience HP Thinclients, I need help figuring out the best host system for our setup. It will be running graphics intensive operations.
I will also appreciate your experience to date, if you have run such setups before.