Originally posted by Dewired The k-x is nothing but the k-m with an included video mode and slightly better ISO performance. The differences between the k-7 and k-x ISO performance are extremely minute and I find myself that the k-7 performs better in low light anyway. (The lack of AF points on the k-x is really annoying). I wouldn't consider it much of an upgrade over the k-m.
K-7 would perform better not because of high iso performance (which is worse) but because of an AF assist lamp and tungsten AF sensor (most people's low light source).
AF points is completely unrelated (albeit I find them mostly useless as 11 and 5-point AF are only better than select AF point in a couple situations where highlighting the AF point does not serve a purpose as one would not have time to respond anyway).
I assume you have not handled both, but the K-x is a considerable upgrade, not just the sensor, but the user interface (not mentioned much, but very noticeable to me), 11 selectable af-points (huge for sports), additional custom functions (bulb mode change), fps, compressed DNG,