To my understanding for a tv less than 50 inches it's a waste of money to spend a bunch of money on a 1080P 40 inch tv if you are more than 6 feet away (which I am).
Eh, not really. With 1080p TVs you don't have to worry about downscaling 1080i and 1080p content and the associated artifacts that go along with it.
Also, am I really missing anything going with a bit cheaper brand?
Look at it this way: a TV is something you're going to keep for many years. Given that, and given the fact that you're literally going to be using it every day, and that you stare at it when you use it, why would you try to save a few bucks by going with an off brand? I don't get it. The whole reason behind going HD is for the quality. So why skimp?
But yes, you probably are missing quite a bit by going with a cheapie LCD. Even some better LCDs have problems like backlight bleeding, banding, poor viewing angles, poor blacks/shadow details, subpar video processing, and innaccurate color reproduction...and likely, those problems are going to be more evident on cheap LCDs.