I don't know about LG, but I have a 42" Sharp Aquos and I really like the picture. I compared it to others in the store (not really the best place to compare LCD screens) and found that the sharp had the best picture quality.
The other thing for the video card, I would go with the 2600XT. That's the card I have I it's far better than the 2400. The 2400 is not able to play 1080p videos correctly.
I was confronted with this decision recently and opted for a 37" Samsung. The 32" models were so close to the 37" ones in price, that 32" didn't seem to make sense. I have a much smaller viewing distance than you, but there is a new stream of thought that with increasing resolution, the ratio of viewing distance to screen size should be reduced.