Thank you so much for all the replies.
I understand that I need a good PSU for 6870. I just wanted to know if my PC has the potential to upgrade to 6870. My main concern is that the motherboard in my PC looks like the cheapest one you can get from the world.
Any motherboard that can run a 2300 will have the same intel chipset, H61, H67, Z68 or whatever. Since yours is working properly today, so not worry. More expensive motherboards will have more features, such as pci-e slots, usb3.0, 6gb sata, and perhaps stronger voltage regulators which are of interest mainly to maximum overclockers.
If you have a pci-e slot for the video card, an adequate psu, and enough room in your case for the 6870, you are good to go.