GFX Under 7k Pci-e x16 ??

The best card available at your budget is MSI HD 5770 @ 7K. Check the details here.

However your system is too weak to handle it. If you are talking about the old single core Athlon 64 bit processors then that simply can't handle the graphics card. You also need at least 2 GB of Ram.
Similarly for handling card like this, you need to have some good PSU or SMPS..your generic local (read Frontech, Intex) SMPS won't be able to handle it.
You need at least a 3 GHz Dual core processor...upgrade to Athlon II dual cores.

Your price tag for GPU is OK.!

But if you need to play the listed games at max resolutions with your current PC configs, you need to change your processor, motherboard, ram, psu.

If you want only GPU - HD 5770 1 gig is a nice choice.

You can play all games listed with your current configs, but at medium settings and medium resolution

@ Op - what PSU do you have ? - you may need to change this if it's not a good barnded one. What's the screen resolution of your anyway ?