May I suggest that you hold which ever camera you buy prior to buying it.
For example I have the K10d - at the time of purchase I had no brand loyalty so I reserched all offerings and was open to all until I held them.
Having handled the camera's I discounted the Canon 400d and 30d, the whole Olympus range and was left to decide between the Nikon D80 and the Pentax K10d - as you can see the Pentax won partly due to the in body stabilisation
Whilst I agree that Pentax may be the right route handle all of you possibilities I think is my best advice.
One word of warning is that I believe that some of the lower priced Nikon bodies have no af motor in the body, if this is true of the latest offerings only lenses with built in motors will autofocus and these lenses often cost more. I am not saying that Nikons are bad it's just that having an autofocus motor in the body of the camera is a must in my opinion - check the model if you do look at Nikons to be certain.
I use M42 lenses and other manual focus lenses on my K10d and love them, I also like my af lenses as well though