Sounds like youll be having a cracking setup. . 50" with 3D at 800....hmmm... all I can think of/see is the Panasonic ST30, Theres the LGs for less but dont recommend them this year, or for over 900 theres the Samsung D6900, another great set and populare on here.
Just to add I sit about 8ft from my 46" and its great, if for largely HD and over 8ft though def 50" will be better for 3D.
No problem ST30 all the way, best to go demo still and see what you think. In two minds a bout the sales, most stuff sold at discount is the stock they cant shift. Comet have raised the price of their ST31 ready to drop back down again, though other stores still have them for around half their RRP at the start of the year.
If you dont notice any dead pixels with normal viewing dont go looking, its a slippery slope. If you must theres some slides you can use, dont know uf Vickster has a link, I cant remember where peoole are getting them from at the mo.