I think you're talking about a NAS(Network Attached Server). Well, much better than usual USB storage. Since you'll have more options and features (like configuring file access permissions, streaming media, blah blah...).
One major issue is speed, since the bottleneck will be the 100mbps or 1gbps network connection. I got one, LaCie (1TB, 400$), which died months ago, so LaCie is bad.
Anyway your best option is to build your own using FreeNAS,
http://www.freenas.org/.
