Noob Build - Efficient/Quiet Build

Hello,

I am looking at building my first HTPC. (efficient and low consumption)
I must admit; I am not really knowledgeable on all the pieces needed and how they all fit. I have been reading tons of information online.
I am looking for a HTPC that would stream HD (720p and 1080p) content that is downloaded. The HTPC would be running a bit torrent client in either Windows or Linux. (If possible this would also replace my file - media server)

I have been looking at the Zotac IonITX F-E http://www.newegg.com/Product/Produc...7;20IONITX-F-E.
Is the ASUS AT5IONT better?

Is there another mobo/cpu combine that would be better.
Any case recommendations with power supply?

Budget $300-$400

Any help and guidance would be greatly appreciated.

Thanks