I see that Pioneer have two 42 inch Kuro models. One is PDP-4280XD - Lower spec and one is PDP-428XD - Higher spec. Can any owner comment on both and is it necessary to go for the higher spec verion considering it has intelligent brightness control - is this necessary? I notice that on the pioneer website the higher spec has this particular feature: - ISF calibration ready: The ISF C3 (or Custom Calibration Configuration) feature allows your screen to be optimised for your viewing environment. As an optional service, a trained professional can precisely calibrate your plasma panel with customised levels of contrast, tint, colour level and other parameters. What would be the difference in picture quality between both if the higher spec has this?