One more point of clarification, if you will. In addition to the Server 2012 R2 Std software, one must purchase CAL's for every workstation that accesses the server?
There's two modes of licensing, Per User and Per Device. The rule of thumb is:
If you have more users than computers, use Device CALs.
If you have more computers than users (more typical in a Medical Office), use User CALs.
So, for instance, in my office, I have 21 computers but only 5 users. It makes more sense for me to use User CALs over device CALs.