Here is the full-size test sample gallery for measurbation (by Pentaxian "Devorama" who has both a K2000 and K-x), the background of the test has been briefed in his main page:-
and also with more shooting information told in his post at the DPR:-
I think the dog JPEG shots are not easy to compare as the WB tones are quite different, although they are the only in-camera JPEG shots. The dog shots give us some idea on how the AWB and preset Tungsten WB of the two cameras behave under that lighting condition, though.
As for the RAW shootout for different ISO speeds, I prefer to inspect and compare the converted images with original Pentax software, i.e., Pentax Digital Camera Utility 4. For quicker and easier view and measurbation on those DCU converted pictures, I re-organise and tabulate them as follows:-
My opinion? It seems both cameras are not bad in IQ and noise control/details retained. I still like the colours of the K-m better but the K-x is not that bad anyway. But one thing is just for sure, both cameras will blow K-7 out of the water so easily or just let the K-7 eating dust in the land as long as IQ is the utmost important thing under concern.
It would be interesting to see how different sensors could affect the IQ performance of different PENTAX DSLR bodies afterall!