secondly the only difference spec wise is gonna be in clocks and the cooling system employed. across the board one can generalize nd say that the cards based on reference design are all the same.
the non-reference cards will be like hte Palit with its custom dual slot cooler nd Sonic edition cards, etc. i’m not too sure about the non-reference models avail in India.
getting the sonic dual edition wud not be a good idea as it would dump all the heat in your case better get a dual slot cooler 4870( ref. design saphire,gecube etc )
You can also go for Visiontek HD 4870 which is also dual slot and I have been using since last 10 days and working fine with very sharp and crisp picture in monitor as well as LCD TV. It is not available in India but got it from KMD.