I have just recently been testing a K-70 for fun (bought it in a lot for the lens it came with) and have been very impressed. I love the K-3, and you really can't go wrong there, but the K-70 feels way more modern with the high ISO performance especially. That means a lot to me since I shoot in low light often. I like the body design of the K-3 better, but if you're coming from the K20D either are going to be a change in layout.
Not sure how the KP and K70 compare and the exact feature differences between them, but I am now convinced that the K70 is a great deal for performance/cost ratio, way better than I thought. It's worth looking into, especially if you have a tight budget and could use that extra cash to get a lens