Slow render on GTX 580 Nvidia Palit brand..

Dear All,

My custom made computer is not performing what I expected. My graphics rendering is not fast or satisfied. I used Zbrush, Cinema 4D, After Effects and Premiere Pro. My Cinema 4D Renderings are very slow. Where do i need to tweak my computer settings. Do I need to go for any better system? What is the best configuration for these purposes with the above mentioned applications. Please give me a solution..

My configuration:

Win i7 Inter core i7 2600k 3.4 GHZ
M/B gigabyte Z68XP-UD3R
RAM (Patriot) - 8GB DDR3 -1333 MHZ
HDD- 1TB + 1TB segate 7000rpm
Graphics Card- Nvidia GTX 580 3GB/ DDR5 (Palit)
Power - gigabyte 720Watts.
OS- Win7 64bit