For lower ISO the K-30/50/500 really can hold it's own in IQ stakes (the ff's will leave for dead after 400). Only thing I have noticed so far between K-30 and K-3 is I no longer have to apply as much sharpening, slightly improving the quality. But the difference is still marginal, These lower spec Pentax cameras really are a bargain, and I'd recommend them to anyone (and have recently created a new Pentaxian with a mate picking up a K-30).
With some good glass, comes good results. Those following the Single in December challenge will have seen this pic of my K-3 taken with my K-30 & FA77.