Originally Posted by rolion
make sure it takes x64 OSes(Windows 2008 upward),otherwise you'r stucked in the Server 2003 x32 OSes only !
Windows is not the only Server OS!
HP have had deals in the last couple of years with their entry level boxes, might be worth keeping an eye out.
If you cannot get your hands on your desired hardware, in the mean time you can get some exposure to the software end with a simple solution such as VirtualBox with fixed sized storage, bridged, whilst following tutorials such as in Serverwatch
is one of many sites worth a gander now and then.
For reference it might be beneficial to create an evernote account and clip the relevant notes which have aided you so you can use these again in the future if needed.
And have fun!