So me and a couple of my friends have been playing Minecraft together on a Hamachi server that I run from my gaming PC. The only problem with this is that I'm not willing to leave the server on all the time, as it take up my precious RAM. We're thinking about chipping in for a dedicated server that could support up to about ten people and that I could run all the time so my friends can play when I'm not there. This would be my second build.
Guidelines
-Very low profile case
-Can support up to ten people with no latency
-RAM should be preferably dual-channel or above
-under $300 budget, $150 is preferable
My Speedtest results were 15.28Mbps down and 1.93 up
Total price of this is $218 dollars. For that you get an APU that would run it at rather high speeds, being 3.7 Ghz, and having room for some overclocking if needed. 4GB of ram, which is more than enough for a unix or windows based MC server. You wanted a small case, and I believe that this will fit that well, and it includes a PSU more than capable of powering what little is inside. I picked a 60GB SSD because I figure that an SSD would be faster than a hard drive you could get in the same price range. The motherboard supports SATA3 and USB3. If you wanted it to feel even more smooth, going from 2x2 GB of ram to 2X4GB would be a nice upgrade, and wouldn't cost but like 10-15 more, and would allow you to host up to 45+ people as far as the ram went.
Minecraft runs in java and therefor isn't multi-threaded. So in this case, the faster the clock speed, the better. It only needs two cores (the other to run typical background tasks), but it needs to be fast to track 20 people in different areas on the server. Next important part is reading and writing speed of your hard drive. I suggested a small SATA3 solid state to reduce server lag for your game. As 10 or more people explore different area at the same time, your hd needs to constantly load new visible terrain and save any alterations people make to the terrain. You could always just create a RAM-disk for the fastest scenario, but I chose not to do it. 24/7 fan noise is annoying, so I would suggest maybe later getting a quieter heat sink for the CPU.
To go with that link is this Intel based build (using the CPU in above bench), which uses exactly the same parts (bar CPU and mobo) and comes out $6 more with 1/2 as much performance on top.
For a game that (unmodded) is incredibly thread restricted, going for a CPU with higher single threaded performance is a far superior choice.
I dont know about you but i have run MC servers off of old pentium 4 systems. I have a slim dell that i used for a server for a friends son a year or so ago and it worked great. 2.8 ghz, 2 gb ram and it used a PCI intel nic card with 3mb up he had some where around 15 people on it little issue.