On an A series lens or newer I auto ISO 100-3200. If shooting in very dim lighting I may bump it to 6400, but noise starts to become unacceptable above that.
IMO, leaving Kr in ISO 200 negates one of the greatest feature of this camera, and will cause undesirable slow shutters to become a problem in low light situations.
Goat in a barn - 6400 ISO with FA 50 F1.4 with ambient tungsten barn lighting (the worst ever)
Kitty in the grass was shot handheld with K300 F4 (manual lens) ISO 3200 to keep the shutter speed above 1/150
Pool shooter is at ISO 6400 with FA 35 F2 with ambient tungsten pool hall lighting.