My dad has a K-7, I have a k20d, and my mom has a k-x. Today, my dad bought himself a k-5 and we would like to sell 1 of the older cameras to cover some of its cost. My dad was thinking of selling his K-7 up until I told him i'd like to have it (though we both agree it's not that much better than my k20d). We're having trouble deciding between the k20d and k-x. The k-x is a lot better for low-light, which my dad finds very useful, and my mom likes its size and weight. The main advantage to the k20d is its weather sealing and larger image size (though I feel the k-x produces a much better image). Which one of the three would you sell?