OK I agree with basically all of the above. The K-x does not do well at ISO6400, I got the best results at ISO400 and under.
There is a setting to allow it to go down to ISO 100 I'm pretty sure, but I can't remember what it is. (and mine is no longer working) Expanded ISO I think, maybe someone who has one can look for it.
I agree with Paul about the settings, go for ISO200, f8, and whatever shutter speed you need for a good exposure. My K-x didn't do a great job at setting the exposure, I always took a test shot and adjusted as necessary. The K30 does a lot better but I still do the same thing.
Look up the settings, I'm almost positive I was getting ISO100 with the K-x, and I kept it set to manual ISO, never auto. I never used anything auto though, I'm a manual guy from way back.
One thing I thought of when you mentioned auto focus, plenty people have found that their lenses didn't focus properly on auto, and had to use the fine tuning option built into the camera. I think the K-x can only handle one lens setting. But you can fine tune the focus to get better results.
For landscapes like the one you posted, try to fix your focus about 2/3 of the way tot he horizon or a little more, and depend on depth of field to help keep things nominally in focus. At f8 it should do a good job. Also once you find the spot where you want to focus, keep holding the shutter button halfway down so it will not change, and if you need to recompose, you'll still stay focused at the same spot. The focus confirmation shoud show when you have good focus, I kept mine set to center weighted, so whatever was at the center of the shot was my focal point. I used the method described above for a lot of my sunsets, with good results.
Do a little looking online, (I'm repeating myself here) and find out the relationship between Aperture, ISO and shutter speed, and how each affects the others. Also look up depth of field. Briefly, the smaller your aperture, the more depth of field, which is one of the reasons f8 or f11 is beneficial for landscapes.
Since you are dealing with landscapes, I'll stick to mostly landscapes, with manual lenses though.
This one was at ISO200, f8, 1/350 with a 28mm lens. (aperture does not show in EXIF with manual lenses, they don't have contacts to communicate that info with the camera.
This was with a 50mm lens, ISO200, f8, 1/90.
This is a crop from a picture my sister took while I was driving, I preset the focus to infinity and made sure the exposure was already right, ISO 200, f8, 1/750. All she had to do was point it out the window and shoot.
Looking through the few I still have from the K-x, I'm realizing I may have been wrong above, the K-x might limit you to a minimum of ISO 200. Otherwise I would have been using ISO 100 for some of these.
And just for fun, an action shot taken with a 200mm M42 lens, ISO200, f11, 1/750 in very good light.
That and the shots already posted should give you an idea what the K-x can do, I wish mine was still working, I'd still be using it a lot.