Print services aren't that resource hungry. It depends really on what they are printing and in what manner.
If this willl be the only role it's performing I'm not sure I would recommend anything more powerful than quad core/4GB ram - as it would just be wasted 99% of the time. Going down to something less powerful, say 2GB RAM and dual core, might just end up squeezing too tight when there is print demand.
Make sure it is on a gigabit ethernet connection, naturally.
This is a good candidate for virtualization really if you already have the infrastucture in place, because occasionally there will be a transient demand in resources when someone prints a photoshop document or massive print job which does benefit from fair CPU and RAM, but the rest of the time, it will just be sitting idle. It is difficult to justify dedicated physical hardware just for a print server role, on the same token putting the role on other servers is also a bad idea, hence virtualization.
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