Originally Posted by TehMac
reason I ask is that I am looking to build a rig for a dedicated server and want to keep it under $400 or so.
Should be fairly easy to do. Single threaded performance is what you need for minecraft since it's a single threaded java application. The more RAM you can throw at it, the better. With 16 GB of DDR3 being well under $100 I'd say that's the minimum you should get. What you'll likely run into as a bottle neck first will be network bandwidth. With 4 people on my server, upstream traffic is around 250-300 KB/sec. So about the maximum I could support with my Uverse upstream being an actual 1.2 MB/sec, is around 15 people. And that would leave little room for spikes in traffic, for example if a bunch of people travel to new areas at the same time.
Also, check out MineOS. It's a distro built specifically for hosting Minecraft and is very light-weight.