the best way to evaluate a tv is read the reviews and then actually go to the stores and check em out urself. opinions differ greatly on what is a good picture and what isnt.
anyway, it seems like Vizios have very good pictures for the price, however they seem to have problems with durability. everyone that i know that has a Vizio panel complains about it after a couple of years such backlight bleeding, dimming, etc...
another tip is to check out Dynex when they are on sale. its best buys inhouse brand, but they dont actually make the panels. they get them from Samsung, LG, etc.. The only down side is luck of draw. Getting a Sammy panel depends on model and even lot number. to check for luck, avsforum is a good spot.