I went from a K100D Super to K-30 (basically the same camera as a K-50). A big upgrade. Apart from all the reasons everyone has given, there is video, focus peaking and the opportunity for much heavier cropping (useful because I often take photos of wildlife and no lens is too long!). The K-3 would give even more scope for cropping. But if you are not likely to crop a lot, 16mp (K-50 or K-5IIs) would be plenty, especially if you don't have a set of high-grade lenses.
You said your husband is "cheap". I'll bet he says "frugal"!
---------- Post added 11-30-14 at 11:04 AM ----------
Originally posted by Kriss I have only the 18-55 kit lens that came with the K100D, and researching new lenses got me into this mess. The one I plan to buy (either now or later) is the Pentax DA 35 2.4.
It's amazing value: light, compact and sharp. But also consider the other plastic fantastic, the DA 50 f1.8, which is light, compact, sharp
and fast. Someone called it the poor man's limited and I'd agree. I now have the FA 77 f1.8 (recently voted the best Pentax lens of all time). As wonderful as it is, it costs 6 times as much, but it's not 6 times better than the DA 50. (Hope I'm not tried for heresy for saying this.)
If you can, get both the 35 and the 50. If you have to choose one, there is a constant debate about which to get first. You can't really go wrong with either the 35 or the 50: after a kit lens, both have the "Wow!" factor. It depends on what you shoot. The 35 is more versatile, the 50 is better for portraits and for subject isolation. Initially I would have said the 35, but now if I had to choose one it would be the 50. The function of the 35 could be served reasonably well by a good standard zoom (e.g. Sigma 17-70, Tamron 17-50 f2.8 or Tamron 28-75 f2.8) but the function of a fast 50 (whether the DA 50 f1.8 or the FA 50 f1.4 or the A50 f1.7) can't.
Think about the kit you would like to have over time and see how the lens fits.