Interesting how much attention goes to the amount of cards he wants to use. As if this would be the only question.
My first question is if frontline2010 did use MediaPortal allready and if MyTv is working well for him.
I ask because all the "US specific" support has been developed by team members located in europe. We sadly do not have anyone from the US in the team who could develop and test MyTv.
So before diving into the hardware questions of the big rig, I would like suggest that you test MP 1.1.0 RC2 first to see if all works as you want it to.