What Rik said, I'm pretty sure even a CS6 license will allow two installs as long as they are not simultaneous. I actually use FCP & compressor to automate the workflow with a Qmaster cluster, so I'm using all cores on my macbook pro and the mac mini at once - although this really works best for huge multi-clip encodes, as Qmaster is sort of finicky.
I have two PC workstations, a mac mini, a macbook pro, and a standalone Synology NAS server with external backup, all hooked up to a 5 switch auto-uplink netgear hub (this one
http://www.amazon.com/NETGEAR-ProSAFE-5-Port-Ethernet-Desktop/dp/B00002EQCW) at 1000 mbps which tops out around 115 MB per second between all machines, which is usually disk-limited. For really demanding stuff I have two 750 GB SSDs in RAID1 that get about 800 MB per second read/write on my main workstation.
The mac mini can use bi-directional windows SMB file sharing and the NAS will read / write easily with mac or pc so it makes my studio platform agnostic. You don't even really need OSX server, 10.9 works just fine. There are a few small things you have to set up right between systems but it's way easier than it sounds. And everything gets archived to both the NAS and a bare external drive every night - I use the drives like tape storage for old projects, 1TB disks are pretty cheap these days.