A very intelligent and precise question, if I may say so. Sandy has given you the answer. Check out the camera comparator tool for more details of each model:
https://www.pentaxforums.com/forums/pentax-cameras-compared/?c1=Pentax+K-5&c...c3=Pentax+K-S2
There are other affordable WR K-mount lenses that might interest you too. Some versions of the DA 18-55mm, 18-50, 50-200 are WR.
If you want to add a telephoto lens consider the HD-DA 55-300mm f4-5.8 WR and the HD-DA 55-300 f4.5-6.3 PLM. The PLM is the better of these two, but it won't work properly with the K-5 series or older bodies.
If the PLM is in consideration (and it is a very good lens), you should look for a K-50 or K-S2, which should be available within budget (they can be used with the PLM provided the latest firmware is installed). The K-30 (virtually a twin of the K-50) is another possibility, but it requires a hack of the K-50 firmware (
Running K-50 firmware on K-30 - Pentax Forums). The K-30 and K-50 use the same sweet 16mp sensor as the K-5 series. The K-S2 uses a 20mp sensor and has a number of worthwhile additional features, such as a screen that flips out, Wi-fi, and no AA filter.
If you go for K-5 series camera (a good choice), you could get the HD-DA 55-300mm f4-5.8 WR. The screw-driven AF is noisy and not quick (unlike the PLM), but the resolution is good and it is quite cheap now that it has been superseded by the PLM.
I have used the 18-135 and 55-300 with a WR body as a grab-and-go kit for years. Great combination for anything that you might happen upon, like two bulls wrestling in the rain.
Last edited by Des; 02-08-2020 at 12:50 PM.