Welcome aboard! You made great choice in the equipment you bought 5 years ago. The K-30 has a lot going for it, especially at the price point. Your kit lenses are decent despite being cheap, and your DFA 100mm macro WR is a stellar performer. Many people would have chosen a cheaper macro lens, of which some are very good, but having the better build quality and WR is worth it. Drippy conditions often do present opportunities for some fine macro shots.
As to WA, the DA 20-40mm f/2.8-4 is a very fine all around zoom lens, having fine IQ, a great build quality, quiet, sure AF, and WR. But, as others have said, not all that WA. I have this lens as well as the DA 12-24mm f/4, which is a very fine UWA zoom lens. Its distortion is virtually nil from about 15mm, and not even bad at 12mm. Now, I'm referring to linear distortion. All WA lenses will present some degree of perspective distortion, depending on distance and the angle from where the shot is taken. Resolution is very good to mostly excellent from 12-20mm, even wide open, and still very good up to excellent at 24mm. Edge sharpness is exceptional in being very good to excellent at all focal lengths. Performance being from f/4 through f/11.
The forthcoming DA* 11-18mm will be 1 stop faster with its f/2.8 aperture, but will no doubt be larger, heavier, and much more expensive, and how well it will perform at f/2.8 remains to be seen. It will no doubt have a quiet DC AF and also WR, though these are generally less important features in an UWA lens. However, a faster f/2.8 can be useful in low light situations, especially where there is movement, such as people shots, where a faster shutter speed may be needed. I'll probably not be in the market for this lens myself, since I have other alternatives for filling any such f/2.8 need- and/or I can shoot with a KP.
This is another aspect you might consider in terms of future steps you might be taking, towards which you could put this cost difference between these lenses. Your K-30 is still a very good camera. But the KP's performance, build, controls, and features are in a different class. The KP's high ISO performance is on such a higher level it essentially makes the DA 12-24mm f/4 functionally like f/2.8 on your K-30 body, and even better yet. You might alternatively pass on the KP's superior build, superior control set, and numerous other refinements, and go cheaper for a K-70, which is very nearly as good for high ISO performance and resolution.
Last edited by mikesbike; 04-25-2018 at 04:17 PM.