If you have any lenses for the Nikons, I'd stick with them. Any of the Nikons would be great, but the Nikons with internal focusing motos have faster focusing capabilities. I'd be happy to help whether you go with Nikon (which I know more about) or any other brand because I can do some research on them. Sorry to hear about your D70. It is a great camera, but whichever newer model you choose, you will see noticeable improvements just because of technology updates. They are capable of much higher ISOs, so they are better in lower light conditions.
For excellent Nikon advice and reviews, I recommend reading Thom Hogan.
Nikon Digital Camera and Photography Articles by Thom Hogan camera reviews on right
2013 Nikon News and Comments by Thom Hogan