Confusion related with New Graphics Card

Hi everyone....I am looking for a new Graphics card...

Currently my desktop has the following configuration:

Motherboard: ASUS P8Z68-MPRO
Processor: Intel(R) Core(TM) i5-2500K CPU @ 3.30GHz (4 CPUs), ~3.3GHz
Graphics Card: NVIDIA GeForce GTX 560
RAM: Corsair Vengeance 12GB DDR3
Power Supply: 550W Corsair CS series
Cabinet: CoolerMaster Elite Series (Mini Tower)

I want to upgrade the graphics card. My budget is Rs 20,000...