Antilycus: +1, Ubuntu Server is awesome for being CLI-only, it's so fast and resource efficient.
I can make a Ubuntu test-VM of a new server on any old piece-o-crap desktop laying around my work, and it will run respectably on any machine with atleast 512mb or RAM, if it doesn't have virt-acceleration. If I decide to move the test VM into production, I can export it, and then import it onto a real VM server, and Ubuntu is smart enough to detect the hardware changes.
If I need a GUI for anything I'm working on, I can just install GUI tools on my regular PC like PGAdmin, Eclipse, etc... and then use Samba shares or the network to connect to the VM.