Best Graphics Card under $150?

Hello, everybody! I am in need of a new graphics card. I was wondering what you guys thought would be the best-of-the-best for less than $150. I would like to play games, and it needs to handle 3D stuff really well. Also, I would prefer NVidia, but if there is an ATI that is great, tell me!

I believe I need a PCIE x16 card.