Install Red Hat Enterprise Linux for Virtual Datacenters on Xenserver?

Hi all,
I want to build a test environment on a single physical, standalone server and run approximately 20 RHEL VMs.
I am assuming that I can install the free Xenserver to provide the bare metal O/S, and then purchase Red Hat Enterprise Linux for Virtual Datacenters, Standard (unlimited guests) to install all my VMs??
Any advice welcomed.

Many thanks,
Mark