QNAP's TS-470 is a solid performer with plenty of features. But the main reason you'd want to spend $1000 on it would probably be its four gigabit Ethernet ports and expandability to 10 Gb Ethernet somewhere down the road.
Naturally, you're not going to realize this NAS appliance's performance potential using mechanical storage across a single gigabit link. In that configuration, you'll saturate the connection somewhere around 120 MB/s. But QNAP also supports link aggregation to enable much higher throughput. And if you're really serious about speed (and less concerned with capacity), you can load the TS-470 up with SSDs, snag that 10 Gb upgrade, and try pushing above the 1 GB/s range.
The TS-470 doesn't need to be a speed demon, though. It's also set up to serve media content straight into your home theater through an HDMI output and suite of software that includes XBMC. Here's the thing, though: there aren't many enthusiasts who want a NAS appliance sitting next to the TV. It's just not the right form factor. We're bigger proponents of the gaming-capable HTPC disguised as a rack component and capable of piping in video content through a gigabit Ethernet connection. If you don't care about gaming, though, and you have a discreet place to keep a NAS, then sure, QNAP's solution does feature hardware and software able to handle that environment, too.
It may be somewhat plain-looking. It may be expensive compared to what you could put together on your own (providing you're willing to put in the software work and validate your own storage). And four hard drive slots doesn't give you a ton of room to grow. But if a 16 TB ceiling sounds workable, and if you'd rather lean on the expertise of a networked storage vendor specializing in NAS hardware, QNAP's TS-470 is capable, quick, and scalable as you find yourself needing additional throughput.