SBS2011 domain containing a W2K3 server w/ 2003 TS CALS a possibility?

I’m trialling SBS2011, however to keep initial CAPEX to a minimum I want to re-use a W2k3 server license with 20 Terminal server CALS if possible (with TS licensing installed on this box)

I know I can install extra servers into an SBS2011 domain. Can I install a W2K3 server into this domain or do extra servers need to be W2K8 R2? and if so can I re use my 2003 Terminal server CALS? as ideally I only need the TS to be based on W2K3 and want to avoid having to buy a W2K8 license + W2k8 TS CALS

thanks in advance

G