I am a complete noob, and I'm sorry if this question is ridiculous but I simply don't know enough to choose on my own.
I am building a rig for doing some video editing ( after effects ) some 3D work ( Maya, 3DS max) and i will probably be running 2 monitors. My budget for the whole computer is around 1500$, so for the GPU i would like to spend 200-400$.
get a gtx 570, it is supported generally and can perform as well as more expensive quadros. It also does much better than the new 6XX in none gaming applications. You should be able to get one for less than $300.