There's no problem with the server design, it's perfect for our purposes, and even if there were problems they would be redundant now as it's already been bought.
Right now we're just seeing if it's cost effective for us to go with VMware. I had planned to contact them, as I'm being told conflicting things about the licencing.
As for how many VMs we'll need and with what specs we'll need for each, we don't know right now. We would set up at least 2 or 3 to start with but in a years time I can't say how many with what requirements, right now our goal is to put a flexible system in place so that we can deal with those requirements as they arise, hence why we'd like insall a bare metal hypervisor as opposed to a regular OS.