What's the best cheap (under $400) server for Linux?

My last server died horribly (don’t ask.) I need a replacement but don’t have that much money. What it does: DNS, web, mediatomb (upnp sever), and file server for macs (using atalk). I also use SQL but only for projects. I’m looking at an Atom dual core CPU something like http://us.acer.com/ac/en/US/content/model/PT.SEM02.011
but not sure if the Atom will do all I need. Any suggestions?