First of all, a NAS is a running computer! Just a bit more lightweight.
IMO a little bit TOO lightweight, especially for the price.
My suggestion anno 2014 is make your own package:
Gigabyte makes a very nice Mini-ITX board for your needs: it is as low on energy use as a decent nas (10 watt!), yet way more powerfull. It is based on the Intel Celeron U1037, has dual gigabit, 3 SATA ports, HDMI out (for direct TV connection, very important if you like 24p content!), and runs FANLESS! Best of all, it is just 70 including processor, so add 50 for 8GB of RAM, 30 for a PSU, and 30 for a case (or build your own box) and you're surpassing any NAS AND APPLETV for just 180. You can add 2 3,5 inch drives and an SSD for storage.
Spec_______Synology DS214+ (290)______________________DIY Server U1037 (180)
Processor_____Marvell Armada XP Dual_1,33Ghz________________Celeron 1.8Ghz Dual 64 bit (same power E7400 C2Duo)
Die_process___40nm_______________________________________22nm (hence more power at lower heat)
RAM_________1GB________________________________________8-16GB
SATA_________2x SATA 3Gb________________________________2x SATA 3Gb, 1x SATA 6Gn
HD_Decoding__no_________________________________________yes (HD2000)
Video-out______no_________________________________________HDMI/VGA
Fan___________90mm (20dB)_______________________________passive
Ethernet_______2xGigabit___________________________________2x Gigabit
PCI_slot_______no_________________________________________yes
Software_______DSM5_____________________________________Windows,_Linux,_OSX
DTSHD-MA_____icw AppleTV: no_____________________________over HDMI
24p playback___icw AppleTV: no_____________________________over HDMI and VGA
(retro) games___no_______________________________________yes