It's claimed that Kx has 12 MP A500 sensor (or a very similar version). There is a 14 MP version in A550 whose samples were posted on imaging-resource.

A550 blows the reds just like Kx. (K7 does this too, so does, to a slightly lesser extent, Canon 7D ). Nikon (D90 and D5000) do much better in this part of image (beating both Kx & A550). This probably has nothing to do with the sensor, though, but with jpeg noise reduction in red channel.

*A550 (on the left) ISO 1600 vs Kx ISO 1600 *

http://farm3.static.flickr.com/2583/4137728746_90a5c97e30_o.jpg

In the rest of image, A550 (14 MP) and Kx (12 MP) are very similar (at least the jpegs).

*ISO 3200. A550 is on the left (kx right).*

http://farm3.static.flickr.com/2507/4137798564_7ee5029ff5_o.jpg

http://farm3.static.flickr.com/2801/4137034879_5c6796d1b2_o.jpg

*ISO 6400* kx on the right.

http://farm3.static.flickr.com/2802/4136315237_fc1272a455_o.jpg

Canon 7D is probably overall APSC champ