Graphics card not performing high performance

[waterproof]

My PC specs:

Intel Pentium Dual Core E5200
Gigabyte S-Series G31M-ES2L motherboard
Asus EN900GT BP Video Card 512 DDR3 (NVIDIA GeForce 9600 GT)
4GB Kingston DDR2 RAM
and I have a 550watt powersupply, I was told when I startup that my graphics card has lower its performance etc to 'low' because of my PSU, now I'm wondering, what sort of PSU do I need? I was told to get a 550watt from a noob and ended up getting the wrong one.

Oh and I'm getting the PSU at this store, if anyone could recommend me which one I should get, thank you.
http://www.arc.com.au/pub.php?gid=23385&p=group

 

[klepto12]

did you plug the 6pin power plug into the video card? looks like this

 

[Rage_3K_Moiz]

The 9600GT doesn't require much power at all. What 550W supply have you bought?

And yes, make sure you have the 6-pin connector plugged into the card. Not having done so causes that message to appear.