The K3 Mk3 is a very good camera. I have the old version. It's an APS model, not full-frame 35mm, which was never a limitation for me. Unless you want to do huge photomurals, you'll never notice a difference. It does have twin SD card slots, which will make your life easier, if you shoot both jpeg and raw files at the same time.
The new model has the upgrades found on the KP, plus dual card slots. It's a bit bigger and heavier than the KP, which likely won't matter at all to you.
Pentax has remarkably good cameras, priced well below comparable models of Nikon or Canon.