lol. This is a lot of work, it appears, to essentially work around the MC GUI which has taken a lot of work and effort to perfect. I also have a 7.1 Yamaha receiver but mine doesn't have an ethernet port on it. What exactly does the ethernet port do? Does your TV also have ethernet? Are the ports supposed to let you play your content? I'd say simply enough that you should consider the TV the main place to messing with content and then it will push the audio to the receiver--or just the receiver. Either way, either one has the ability to get the sound and picture (if you pass video through the receiver) so it looks like you need to pick one and use it (which ever has the best interface).
But like I said, it's MC--a Windows application. Maybe you'd be better off just running a desktop computer which is how MC is somewhat intended to run--in Theater mode. It's unlikely that the Yamaha or HP solution will be better than MC--especially when it isn't designed specifically for MC but rather, some junkie Windows Media Player type program.