Yup. Many choices in the line. Rebels, 70d and 7D are the crop sensors. 5D and 6D and 1Dx are full frame. Don't ask me what the differences are with all the different Nikons. I'm a Canon guy :)

If your willing to start all over have you looked at Micro 4/3rd Camera's
Excellent glass are a manageable price point

Try weighing an option of keeping existing camera and investing in better lens instead.. Cameras come and go, where lenses stay with you for long years, if you find the one you love.
Newer camera will have more software and processing power in it, other than that you will get same what you have now.

seriak,

What was your final decision? Did you stay with Canon?

My wife and I just bought a 70D to replace our old 40D. I am impressed with the 70D. We also had a 5D mki and sold it too. The reality is that most of these cameras are more than you will need. We really only upgraded for the HD video. The reviews on the 70D are very good. In fact there are things about the 70D that I find more attractive than other cameras.

Couldnt be happier.

aside from what everyone else has said. The articles I've read and photos i'm observed: without getting into photoshopping, nikon's have better color without flash = good for scenic shots or nature whereas cannons are strong on portrates and flash photography.