Here the system needs to choose. If you then want to dramatically expand the set of optics, to buy a flash and other stuff, you can be surprised system Canon, Nikon and Pentax are very different. Under cheap optics from Pentax understand what bad optics from pentaks almost there. That is roughly the budget of the segment of optics is almost there. Everything besides pentaxa great compatibility with old lenses. The Nikon has several lenses burdeny (for example DX 35\\1.8), but all that higher level — is already just insane money.
Total, Pentax K-x:
stabilizer for any optics, even for excavated in the closet Helios 44-2;
— Matariki AA or AA batteries;
— sometimes not very fast and accurate AF (but frankly not yuzal nikon);
— work with any optics ever produced pentaxim with the best possible set of features.
— should be the normal autofocus from Nikon;
— good selection of Park of optics, with one exception that is not AF-S optics will not autofocus, and extra-budgetary optics costs are astronomical money;
best choice external flashes among all the brands;
— the autofocus in video, which should be noted, pretty useless in real life.
Talking about colors and stuff, I think it is useless. How many people, so many opinions. In addition, the RAW processing can easily equalize the chances of the images.
From himself only add that taking the time pentax k-x fell in love with him. Yes he has his faults, but they are usually visible in comparison with top-carcasses other brands, while within the field more than normal. And Yes, read the Pentax club, there are many good and interesting people who can give a lot of information for thought.