Peter,
if you go with a Samsung DLP, you'll want to keep it at least 3 or 4 inches from the wall behind the set so the fan can dissipate the heat adequately. The 50" Samsungs range in depth from 10.6" (HL-T5076), to 15.1" (HL-T5055). At 13.4" are the HL-T5089, HL-T5087, and HL-T5075. So you can figure that your screen will be roughly 18" to 24", give or take, closer to the seating than the wall. That would put your seating distance at about 13 feet. All the 50" Samsung DLP TVs are around 45" wide.
According to this
HDTV Widescreen Seating Distance Chart, the optimum seating distance from a 50" 1080p set is around 6.5 feet, and from a 50" 720p it's around 9.8 feet. So, at 13 feet you wouldn't be able to realize all the resolution a 1080p set can offer. Thus, a 720p set would be just fine and would save you some dough.
You can find the 720p HL-T5075 at BestBuy, ON SALE right now, for $899 (regularly $1200), at at Circuit City for the same price. Interestingly that's the best price I can find with a cursory search. The next best I can find is $999 at Vann's.com. The 1080p Samsung DLPs (5076, 5087, 5089) are gonna cost more, of course. The best price I can find for the next step up, the 1080p 5076, is around $1200 to $1300. Of course a 1080p set is going to be more "future proof" than a 720p.
I've been really very happy with my 1080p Samsung HDTV. Yes, I spent an extra $450 to have it professionally calibrated, and I consider it money well spent. But, that doesn't mean you would have to do the same.
You might do some searches for 50" LCD sets. You might find one or two 50" models on sale near your budget.
Good luck and good hunting.
