Hi skimble,
Just a few comments (I might have missed some details because I skimmed through this thread). If the ambient temperature above your fireplace is in the 90 to 100 degree F range when a fire is burning, don't mount your plasma above the fireplace. The latter also may place the TV too high for comfortable viewing.
Is your plasma's native resolution 720p or 1080p? That will affect how close you can sit without seeing individual pixels. I find sitting as close as 6 feet from my 50-inch 720p set a bit too close. An ideal range for 720p 50-inch is about 8 to 12 feet.
If the display is 1080p, you could view it from 6 feet and it would look great.
You should set your cable box's internal menu so it outputs the native resolution of your display--720p and 16 x 9--or, if the display is 1080p, then set the cable box to output 1080i. You want the fewest scaling and conversions possible for the best picture quality, and HDMI isn't necessarily superior to component video. If you get superior image quality going directly from the cable box to one of the inputs on your display, then use that connection.
Regards,
Alan
