Unless your home server will need to do A LOT of processor intensive number crunching stuff (it almost certainly won't!) that Athlon 3000 is way overkill considering the bandwidth bottleneck you are working with.

Best use an old laptop or build a Eden / Pico / Mini ITX system that only draws ~20w under load.

As for distro, I assume you can't afford MS Server 2003 but still want something simple. Ubuntu Server Edition is a v.quick way to get an Apache/SQL server running, it's easy to use (for linux) and quite secure out of the box.

r0g