The 4-bay NAS market has a few very good products and many very poor quality, low cost units. Sifting through the sand to find treasure can be quite a task when shopping for an entry level NAS. Also, making shopping even more difficult, many of the NAS products on the market now share similar hardware specifications. One way to remove a large volume of products from your shopping list is by looking at the processor inside. If you don't see Intel Inside or a manufacturer doesn't list the processor type, mark it off your list. The Marvell based units just don't perform as well as the Intel NAS products, even in a single user environment.
In our single user tests, the Asustor AS-604T performs well and slots right in with the Thecus N4800 and Synology DS412+. The feature set matches the N4800, but even though Thecus has been around much longer than Asustor, the AS-604T matches Thecus' software package. In testing we noticed that Asustor already has nearly 100 software add-on features that can be easily installed from right within the NAS's software layer.
The price is the same deal. The AS-604T fits in between the more expensive Thecus N4800 and slightly less expensive Synology DS412+. Personally, I like the AS-604T's user interface a little better than Synology's, but at times I found it so simple to use it was complicated since I'm use to more complicated software. If the AS-604T is your first NAS then you don't have the experience with complicated software to begin with so the Web 2.0 style interface will come easy. I guess the easiest way to explain it is when I, a Windows person through and through bought an iPad. Sometimes simplicity is complicated when you come from complicated and are accustomed to it.
In our small office, multi-client testing, we found the AS-604T performed well up to 24 clients where it peaked in throughput. This is also the point when the latency started making large jumps with each new eight clients added to the test.
The Asustor AS-604T is a quality NAS that's built by an experienced group of NAS developers. If you're shopping for a 4-bay NAS, I wouldn't hesitate to put the AS-604T in the same high category with the Thecus N4800. If you plan to connect your NAS to your TV, I feel the Asustor NAS units with the Boxee software are better than any other NAS we've tested as a media center.