Originally posted by: Chris
I find the tighter pixel density of the 40" to look better. If you're only going to be 6 - 7 feet away from the display I'd go with the 40".
6 feet from a 46" is still well below the point at which 1080p is too low of a resolution (you could have a 50" at that distance). OP, I would go with the larger set if you have the room. If you get a TV that seems "just right" the day you bring it home, then that same set will be too small 6 months (or less) from now once shrinkage has occurred. It was a huge jump from a 27" CRT to a 50" plasma, and it definitely looked big at first; however, after 6 months it looks just right. I sit 9 feet away from it, and even though it's "only" 768p I never notice any pixelation or a less-than-stellar picture from the resolution being too low.
There's definitely a difference between those two models. However, you have to ask yourself which you'll notice more: the bells, whistles, and possibly better PQ on the A650 or the extra 6" on the A550.
Here's a calculator that will allow you to compare the sizes of the two sets side by side.
Edit: Another idea is to cut out a piece of cardboard the size of one of the TVs (including the bezel). Then spray paint the area of the screen (per tvcalculator.com) black to show the area that will display the picture. If you do that with the 40" and it looks too small in your room, then that'll go a long ways toward helping you make your decision. It's so hard to see how things will look in your room until you actually get them home. You could also see what CC's policy is on TV returns/exchanges. If it's the same as Best Buy, then you'd be able to try out a TV and exchange it for a different one within the first 30 days at no charge.