Pixel Shader 3 games are not an issue, as that is down to the client pc to do all the rendering.
If your just going to host a small web site/forum for a gaming clan, a bit home streaming then go home brew.
All you need is a decent spec quad core system, 8GB ram, SSD for O/S and a minimum of 4 HDD's in Raid-10 for data.
O/S can be Win7/8/SVR, web server can be IIS or Apache based.
Of course, you need to ensure you have dynamic DNS setup in your router so the server can be seen by the outside world.
Security, so your server cannot be taken over/corrupt etc etc.