best gpu 2015

My PSU is this: Cooler Master Thunder 450W 450 Watts PSU - Cooler Master : Flipkart.com Its 450W and has 1[6+2] pin power connector. my requirement: -->1080p Gaming @60fps high -to- ultra [no MSAA], [no 4k or 2.5k] -->Should last for 2-3 years -->I rarely play FPS, but usually 3rd...