Tom,
A client of mine has purchased GSX Server to use as a build/staging/test environment. They idea is that it should support a low-volume intranet site just fine, but despite installing the software I honestly can't say I know how it performs from first-hand experience (we haven't installed anything on it yet)
What I do know is that VMWare introduces about a 30% overhead on your box. Another way to look at it is that your 2GHz server will only operate like a 1.25GHz server. That's really not a big deal - with Moore's law, you're essentially rolling back the clock ~6months on your hardware.
Given that fact, and the fact that VMWare sells the software to support exactly the scenario you describe (running low-volume production systems on consolidated h/w), I would say you shouldn't have a problem.
I'm not sure if you can download a demo... but the software I have installed (GSX running on W2K) looks a lot like they just slapped a perl API on top of their workstation product. I would say if the VMWare workstation product supports the load you're expecting (find out really quickly with my VM), GSX will be fine.
