You are willing to ship things based on this build, so don't be to quick to dismiss. eBay, Craiglist, and other regional list sites are the go to places. Say you spend $400 USD equivalent on an older Opteron system and a generous $200 to ship it. You're still coming out ahead and would have a higher quality engineered system IMHO. Just something to consider in the future.
NAS, backups, web development, etc aren't going to stress an atom. I/O will be your enemy far sooner in most conceivable server scenarios until wide RAID arrays or SSDs enter the picture.