Windows based Media Centre - seeking advice.

I currently have a Windows 7 box in my living room with a Blu-ray drive and it's hooked up to my 1080p TV via HDMI. I use SlySoft's AnyDVD HD to watch my BluRay collection on it without problems (everything is legally purchased. I just find this program very useful to ensure no problems and to strip unwanted features). It's also got a Asus soundcard with Dolby surround hooked up to my really nice speakers via Optical.

The box is being moved into my study to be my dedicated work box and I want to make a nice, little media machine in its place that does the same and more if possible.

First question - I'm intrigued by SmartGlass. I'd really like to be able to control the box from my phone. Is this only Xbox or is there any way I could control a Windows 8 PC from my phone in the same way?

Second question - where are all the Retail versions of Windows 8? All I can find are OEM versions / System builder discs. Is this the new Retail version? I have never liked using OEM versions of OS installs. Am I safe in using a "System Builder" disc if I want to change my hardware later?

Third question - what do I use for hardware? I have a Hudson M1 board with integrated processor which I currently use as my home server (because it's very low-power and has lots of SATA ports), but I'm thinking of using it for the media centre. However, what I'd like is to buy an updated version with a Trinity APU but I can't find a fanless on-board version. Do they not exist?

I realize that's bunch of unrelated questions and some might be tricky. So if you can't answer them, please feel free to just post what your preferred build for a home media cetnre would be?

Loads of thanks if anyone replies,

Harmony.