Patriot Memory's Javelin S4 Media Server ($400 as of 08/29/2011) is a four-bay NAS enclosure with a reasonable set of multimedia features. However, the Patriot is pricey given that it lacks the maturity and finesse of comparable boxes such as those from Synology and QNAP.
The Javelin S4 has a rather plain, nondescript design: As a white box with a hinged front panel that provides access to the four quick-change bays, the S4 looks better next to a Mac than to the usual black PC. Apart from its rather cheap plastic drive trays, the unit seems solidly built. Ports include two USB ports on the back for attaching storage and printers plus a single eSATA port. The S4 supports 3TB drives, so its total possible capacity at this time is a pretty hefty 12TB.
As you might gather from its full name, the S4's strength lies in its multimedia serving. It supports iTunes, is DLNA-certified, and even supports Logitech's Squeezebox. In my hands-on testing, it streamed everything I threw at it, including high-definition video, smoothly--not unexpected with a unit that managed 58.8 MBps reading files off its disks in my tests. Unfortunately, the S4 is rather slow writing data; it managed only about 27.7 MBps. In practical terms, these results make this unit a good file and multimedia server, but not great for backup.
The S4 has the requisite feature set, with decent backup capabilities as well as support for bittorrents and Web access to your files. However, the interface is nowhere near as facile as that of QNAP, Synology's windows-in-a-browser, or, to be honest, most of the rest of its rivals. Copying files one at a time in the S4's Web File Manager is particularly painful.
In the end, the S4 is a solid, if not perfect, effort. At $250, it might cut the mustard. Priced the same as the decidedly superior competition? No way.