Which graphics card should i buy?

Look at the graphics card roundups on the main page. They have a best value section.

I recommend any card above $200 basically. Going too expensive won't benefit most games (an HD5870 maxes out many current game settings).

You should probably get a card that's easier to return. It sounds like you have a few options.

If it's possible, and your motherboard supports it, consider going SLI with a 2xGTX560 setup which provides excellent value. The GTX 560's have just been announced.

Don't get a dual-GPU AMD card. Dual-GPU's perform exactly the same as Crossfire and NVidia is better at multi-GPU setups. Also, splitting to two cards means it's actually quieter than one HOT card with high speed fan.

So, to summarize I'd get either:
1) HD6870 1GB or greater (if one card)
2) GTX 560Ti or greater (if one card)
3) 2x GTX 560 OR 2x GTX 560Ti (for SLI)

I'm tempted to recommend just the GTX 560Ti if possible. Anyway, there's lots of reviews.

***YOU NEED A MODERN 64-bit HIGH-END SYSTEM TO SUPPORT A GOOD SLI OR CROSSFIRE SETUP. (at least Win7/Vista x64, 4GB DDR3 1333MHz, i5-750, motherboard support and PSU of 750W or greater)

GTX560s are over 200$ and prices in South Africa are higher than in US/China. OP: Take a look @ ATi 5800 series, they are quite cheap now and provide enough performance even on high resolutions.