People have listed the options. See the DSLR comparison tool for more detail:
Pentax K-70 vs. Pentax K-1 vs. Pentax K-3 II - Pentax Camera Comparison - PentaxForums.com
I went K-30 -> K-3, which I got second-hand for an excellent price. The K-3 or the K-5iis seems to me the value models at present. These are flagship models. They don't always have the very latest feature set, but have many little extras that add up to a lot. For one thing, they have a metal chassis rather than plastic - this makes them a little heavier, but much more durable (and they are rated for double the number of shutter actuations). They use a larger battery, which provides more power for faster autofocus and more shots. They have more dedicated buttons - e.g a button for ISO - rather than having to use the four-way controller so much. And there are many small extra features. Many people like the top LCD. One I particularly like is the far superior anti-dust system: I have had endless problems with dust in two K-30 bodies, but only once got dust in the K-3. And while the K-30 did all I asked of it, the quiet shutter, and faster and more accurate AF on the K-3 have been a revelation.
A camera with a 20mp sensor or better still 24mp sensor is a big advantage if you crop a lot. Also, after having a camera without an AA-filter, I would never buy another with one: resolution is notably better without.
If you want one of the lighter-weight models, the K-70 takes many of the best features from the previous models - flippy screen from the K-S2, 24mp sensor with no AA-filter from the K-3 - and adds incremental improvements to video and other things, in a light-weight body. It's kind of a K-3 Lite - more bling (maybe it is unfair to called the flippy screen bling - it could be very useful), but without things like quiet shutter, top-of-the-range AF, improved dust control, 2 SD card slots and greater durability and more solid construction.