Among today’s new APS-G generation, the K5 is certainly a solid choice, along with the D7000 and the A580, although the Sony Alpha model does not have such an impressive dynamic range compared to the other two at low ISO speeds. All three sensors have solid color depth and good low-light behavior, too. Choosing one among them will certainly be influenced by considerations other than the pure image quality, which for all three of them is very good.
The a55, however, is different. The translucent mirror used in that body is an improvement if you intend to use your camera to record a lot of videos. But it is a slight handicap if you intend to shoot high-quality photos. Sony clearly made a choice —improving the video functions — that has a noticeable impact on still photo quality. But even with still photos, image quality should be very close to a Nikon D90, which is a pretty good performance.
As for the EOS 60D, its sensor ranks last for all metrics. Its biggest problem is, of course, its high ISO performance, which is inferior to that of the a55, even though the Canon uses a standard mirror technology.