If you need a server for your clan's gaming, you don't want to buy a computer. Because then you'd have to learn about using all this complicated software and pay for a really fast connection, and you'd be spending hours configurating it and it would be a constant hassle.
I run the most popular Enemy Territory server in the world right now, the IP address is 18.104.22.168, and I use http://www.gameservers.com
as a hosting provider. All you have to do is pay them, and tell them what game, and you get FTP access to the server to config it, or you can be a noob and ask them to but it's really not that hard.
What game are you guys playing? If its an ID based game I can probably help you if you need it.
For a 40 slot server and a clan website, it costs me $62 a month.
Start asking for donations.
But, if you are more experienced and have LOTS of money, we can help you build one that will serve you well. A dual Opteron 275 system with 4gb of ram should be able to host around 6 or 8 40 slot servers and a website no problem. Gimme a holler if thats what you want, but keep in mind that you'd need a really really fast connection. I'm not talking cable or DSL, you'd need at least 100mbits per second, a T1 is 1.54mbits just for comparison. You'd be looking at spending like $2500 a month just on the connection, not to mention the $3000 for the server build.