There have been a few posts lately about the Atom. The mobo in your link is uses the Atom 510 chip and you might be better off going with the Atom 525 which I think has a bit more power....maybe checking it on PassMark will give you some ideas of the differences.
I have read on this forum Plex (and transcoding) on the Atom is not a good idea. It's better to move up to Sandy/Ivy Bridge for it.
Search for DirtySanchez's Landfill system.
Thanks found the thread will use the CPU/RAM/Motherboard he has listed
CPU: Intel Ivy Bridge Core i3-3220T Dual-Core Processor 2.8 Ghz 3MB Cache LGA 1155 35W
Motherboard: ASUS P8H77-I Mini ITX Intel Motherboard
RAM: Kingston HyperX 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800)
Any suggestions on 1U power supplies that will work with this Motherboard?