The vast majority of the LCD tv's is made by one single company in China, and in most cases your paying for the brand name and a few extra features the company, IE sony, Samsung, paid extra for to have their brand stand out a bit more thn the others to trick you into thinking they built their tv, and they are the best because you get a few more inputs in different locations, and a few menu features, but the min lcd screen itself, maybe not the casing, the pcb board, just the screen and its guts, come from one Chinese builder thats sells the screens to OEM and sell off at a much higher dollar because it will samsung on the front of it.
But if you look at this chart you will see that NOT all of sammy lcd's are made by sammy, and by looks of it only Sharp makes their own screens, and makes some for even Phillips, so long and short of it is, like I said, you buying the name on the tv, but the screen inside is the same pretty much for every tv you see on the shelf at the store
So chances are great that this tv will look, and last as long as the "name brand" tv's, just cost a few hundred less because it says Dynex on it, just may not have as many fancy features as the big guy names.
And this holds true for pretty much ANYTHING you buy, most cases its one company that makes them, the internal guts, and the OEM guys ask them to change the case around, use a different chip, but once it gets slapped on it with a name brand the price doubles or triples in cost, because your again, just buying the name.