3db, you can try all of the options. Take an afternoon and move the speakers to all of the locations, and see if any of them simply sound better.
At 10 ft, THX recommends a 90" screen. To duplicate my preferred viewing angle, it would be a 106".
I'm not saying to get a 100" screen, but I just want to put in perspective that a 52" is not overkill at 10', let alone at a further distance. Just like I said in your other recent thread, get the biggest plasma you can possibly fit.
The resolution offered by bluray is something to behold. Really. It would be a shame not to be able to better take advantage of it by skimping on viewing angle, IMO. For example, here are some controlled comparative screen shots between DVD and BD of the cartoon
Monsters Inc.
It might take a little time to DL the link, but when you do, click on the "show" button.