If you are a true DIY and can go with out the hard buttons you may consider a look at Charmed Quark. Paired with maybe a Samsung Touchscreen 7" PC? I hope you have free time.
http://www.charmedquark.com/

Otherwise, RTI is probably the way to go. Maybe even Crestron if you want a good 2way interface for Itunes and Media Center. Autonomics.

They have a 2way for RTI too but I havent used it.
[Link: autonomichome.com]

We all like to tinker but when you get into a control system this nice you are better off leaving it to people that have been doing it for years. I know most hate analogies here but this is kind of like buying a Mercedes and changing your own oil.