hey, if u can strech ur budget, u HAVE TO buy the ATI 4770(not 4670).
It is a LOT faster than the 9800GT/8800GT. It even pawns the ATI4830. It comes very very close to the ATI4850 and when u OC it its even beats the ATI4850. U can BUY it frm techshop.in for 6.5k. Its the best ever deal out there. U can not go wrong.
Its the RV790 in 40nm with DDR5 memory. Its highly overclockable and runs cool. Its power consumption is low. Just go 4 it !!!!!
here is link:
MSI ATI Radeon HD4770 R4770-T2D512 512MB GDDR5 Graphics Card -
this card will easily get u 2-3 Times the performance of a 8600GT.
do not even think of a 8800GT/9800GT with this around.