Which dSLR is good for video, and has a variety of lenses (old, new)?

I've had a nikon D3000 for some time and I want more freedom to take pictures, to be able to control more settings manually, and I also want good quiality video. I had the D90 in mind, but I'm also thinking of buying some lenses. I'll be shotting portraits and street photography mostly, and I'd like to get a very shallow DOF. With that in mind I looked for the pentax K7, qhich according to what I've read uses M42 lenses. Those are cheaper, and that means I can buy more, and I have more options. I know cheaper it's not always good but I found some GREAT Tamron and Mamiya lenses each for under 100 bucks! Besides the video is good. Which one should I go for? Is there another camera that could do the job? Should I stick to the Nikon?

I have a nikon D90 and a nikon 35mm f1.8 and love it for portraits and street photography and it has a pretty good video feature as well.

Yes, the D90 has a HD video feature.

Jumping to a different camera system is not only not recommended, but is very expensive

The K7 Pentax uses K-mount lenses, NOT M42

The D90 can use all of the Nikkor lenses made since about 1977 and you can find AI lenses at very low cost in many camera stores that sell used gear.

Here is a complete list of lenses made by Nikon and the cameras that use them

http://www.kenrockwell.com/...y-lens.htm

For portrait photography, you will want to buy a 50 mm f/1.8
For street photography, a 35 mm f/1.8 will work

The longer the lens, the better control over DOF you will have

Have a look at the Nikon D7000.It has a plugin for an external mic, which is very handy… And it also allows you to adjust audio levels. If I weren't a Canon person, that camera would be appealing to me for its video features!