rebuild or new machine for a server

So I’ve got a rebuilding thread going on ([url=http://www.missingremote.com/index.php?option=com_smf&Itemid=198&topic=1922.0]http://www.missingremote.com/index.php?option=com_smf&Itemid=198&topic=1922.0[/url]) and the wife mentions just buying a new computer…

If I was to go that route, and considering I would still use SageTV with a computer client, what would be good options?  The last time I bought a prebuilt computer was 2002 or so.