But I assume you still need to run your cables if your main PC is in another room? I can't see 1080p running too well over a wifi network if the router sits upstairs
You can use wireless but anything hardwired will always be better.
Buy a powerline adapter. They're awesome devices. I used to use one before I put ethernet wiring in my home. You just plug one end of the adapter into a power outlet and run an ethernet cable to your router, then in the other spot in your home you'd plug an adjacent adapter and run the ethernet there to your TV, BluRay player, DLNA device, etc.
I have a few Android devices like an Ouya that I have Plex and Netflix on, as well as XBMC. I've also got a Raspberri Pi with XBMC on it. XBMC works really well and you can throw it on just about any electronic device. Even my wife knows how to use it without any trouble so it's pretty nifty.