I work on Autocad also and have used practically every mouse in existance. To me Autocad is very much like gaming in that it requires alot of quick, precise movements all over the screen.
After using low res, 800 to 2000 dpi mice for years, I bought a Logitech G500 and started trying higher dpi, 3200 to 5700 and found the higher resolution to be much better suited for the 27" monitor I use, covering the entire screen with much smaller mouse movements.
Also I like a simple, comfortable, high quality mouse without a bunch of bells and whistles. Left, Right click, back and forth buttons is all I need.
I'd suggest the following in no order of preference:
Logitech G600 if you want to program keystrokes or macros
Corsair Vengence M60, my current favorite
I'll second the CMStorm Spawn, great little low frills mouse with excellent tracking.