I would agree with most earlier posts. I have a K-7 and I have no issue with low-light shooting. I simply do not understand all the fuss about high ISO noise. I shoot in low light conditions and I do not care about ISO as long the noise is reasonable.
I do often some outdoor shooting at dusk incl. sunrise, sunset and very low light incl. nighttime.
From my experience in low light conditions, I tend to use one of these three techniques with my K-7:
1) I shoot JPEG straight out of camera with NR
"Off". Then I process with a Noise Reduction software (Noiseware Standard Standalone). The NR softwares like Noiseware work best when the image files have not had any previous NR processing.
2) I set my USER mode such as I shoot JPEG straight out of the camera with "Strong" High ISO Noise Reducation. The In camera noise-reduction minimum ISO is set at 400. This technique (2) is the one proposed by
Adam in [1,
K-7 High ISO Success!].
3) In very low light I use the fast prime lens: Voigtlander Nokton 58mm f1.4. I bought this fast prime especially for low light outdoor conditions and it is a beauty.
Recently I shot at sunset some waves (ie dynamic motion). With my DA18-250mm, I had to stop at 19:20-19:30. I swapped to the Nokton 58mm and I was able to shoot until 19:50 at ISO 100 to 400, and I took my last shot at 20:10 at ISO 1600.
I shoot typically JPEG in P mode. (Yes, that is very basic but does fulfull my needs.) I set the mode dial to P for (1) and (3), and USER for (2). I use (1) and (2) with my DA18-250mm. In addition, I set the maximum ISO to 3200 in the K-7 in all modes.
Lastly, on K-7 and noise reduction (NR), I would recommend you to read a few relevants threads/discussons in the Forum including these:
[1]
K-7 High ISO Success!
[2]
K7 ISO 2500 noise setting and post processing tests...
Hope that the comments and experience will help....