OK , took the advise into consideration and modified pics. New Pics below.
Main speakers are 2ft in from the side walls, Plasma is dropped to just over 3ft from the floor.
Rear speakers are mounted 5ft high and 2ft from back wall
Thought about this some more. So far I can work out that all I need is a power outlet behind the plasma. As I have the DVD player, my yet to be built HTPC and will have the XBox running through my AV Receiver and will utilise the monitor out to run the plasma.
So this means I need to run 2 video signals from the back of the room to the front - one HDMI from the HTPC for the High Def stuff and another from the Receiver for the rest of the video sources. The AV Receiver options for monitor out are RCA, S-Video or Component. A monitor (Plasma) connected via RCA and S-Video allow you to view the Receivers settings on the monitor whereas monitors connected via Component out don't have this functionality. I like this option as its easy to see what you are doing as the amp's little display means I would have to get out of my chair to follow the prompts.
1. How much better is the picture from composite over S-video?
2. whether i run the S-Video or the 3 RCA's, is it OK to run a video source cable the 10m run or should i look at converting it to Cat5e using one of these converting device?
this is getting me really confused.. anyone know of a software application that you can use to lay out all your wiring needs?