The K2000 has a pretty good noise profile for an entry-level camera, as long as you take the camera off its default Bright Custom Image settings; this setting bumps up the contrast and sharpness which exacerbates the visibility of color noise. Using this setting, you probably don't want to shoot above ISO 200. Using the Natural setting, however, and with the right scene content, photos remain pretty usable up to ISO 1600.
The lack of sharpness in shots like this seems to be the result of blooming in the red channel rather than any problem with the lens. No matter what I tried changing--white balance, ISO, sharpness, changing focus distance and focal length, flash and so on--I couldn't get a sharper shot than this. (1/60 sec, f5.6, ISO 200, auto white balance)
The K2000's pattern metering handled this difficult situation pretty well; normally I'd have used spot metering to get the dark doorway. While my subsequent spot-metered shot was a bit brighter, this is a fine automatic result. (1/80 sec, f10, ISO 200)
The default Custom Image setting, Bright, produces images with surreal, incorrect colors and overly high contrast that really compresses the dynamic range. The top photo was shot with the Bright setting; the bottom the simultaneously captured raw DNG file. For shooting JPEG, the Natural setting produces a much more usable image.