I recently made the move to Nikon from Canon, selling off a 5D3, 1D4, 24-105, 70-200 2.8 II, 400 5.6 and a couple other items. Thus far, I am relatively pleased with the Nikon system.
As you have researched, selling used and buying used makes you breakeven, buying new costs a little out of pocket but maybe worth it for the warranty protection, which is better than anything Canon offers.
Glass wise, they're pretty even in the upper levels with Nikon's lower end stomping Canon. Based on what you are shooting, you'll likely see no difference.
When I switched, I made the choice to go D800. Little heavier than the 5D3 and a little beefier. Excellent camera if you can deal with the large files and the slow FPS. Other than, top notch. I have since sold that body and am looking for a D600 - less beef, but smaller files and higher FPS (important to me). Either camera should be as good or better in terms of higher ISOs, which your current setup should be able to do well also.
Overall, my switch has been a positive one and I am enjoying my new setup. Be prepared for a learning curve as Nikon does things differently, but it shouldn't be a big deal for you.