Originally posted by cls Well. For a lot of reasons, and after MUCH research, I have settled o the K3iii! The order has been placed, and now I just must wait for it to get here, along with a used DA*200 f2.8 that I couldn't pass up (though I am watching for a 70-200 f2.8!). Thank you everyone, for the input. I am super excited to see where this can take me, while I wait for the K1iii! I'll have to clear off the shelf and hopefully find a home for my K1000 and a few lenses in the near future.
Great choice. I've had the KP for several years, and now the K-1 II for a couple of years. Both are great cameras. I still have my K20D in perfect condition, and use it on occasion, especially for Fall color shots due to its extra-rich color performance, as well as my K-5 IIs- still a fine performer within its limitations. I use my KP most often and definitely when needs are more in the telephoto range. The K-1 II is my go-to when within the wide angle to short tele range, and when compact carrying is not a particular consideration.
As to a fast 50mm for portraits, etc. the DA 50mm f/1.8 plastic fantastic is really quite good, or a used "F" 50mm f/1.7 is a great choice as well. I've seen some in tip-top shape at reasonable cost.
I do understand regarding the handiness of the built-in flash for grab shots and for daylight fill use. I have and recommend the little AF 201 FG WR hot shoe flash, as it is very compact for an easy carry-along. It also has a tilt feature up for ceiling bounce or down for closeup work.
Great choice also for that DA* 200mm f/2.8 lens. I've had one for quite some years now, and it is a wonderful lens. If coupled with the DA 1.4x TC, you then also have very near to a DA* 300mm f/4 as well, without having to buy yet another (even heavier) expensive bulky lens to carry. This 200mm lens was my choice over a 70-200mm f/2.8 because it is much lighter and less bulky for use when on camera. Instead, I sometimes couple it with the DA* 50-135mm f/2.8, which is remarkably compact. This combo makes for much lighter, better handling than a 70-200mm f/2.8 and you get more range at the short end. The DA* 200mm lens is actually cut for FF use, but I have yet to use mine on my K-1 II, because the weight factor is far less on my KP, even with the battery grip installed, and the KP is so close in IQ, and with that lens can produce results reasonably close to a 300mm f/2.8 on the K-1 II at a fraction of the weight and expense.
One other factor supporting your choice for the Pentax K-3 III over switching systems, you still have in-body shake reduction technology instead of in each individual lens. So when you buy even an old lens, such as that "F" 50mm f/1.7, it will automatically have SR! A very important factor, in my experience.