What's your overall budget? Why do you need to upgrade the CPU cooler? How much is the CPU cooler costing?
My budget is Rupees 11000
Cooler Master EVO 212 @ Rs 2200+Tax
HD 6850 @ Rs 9500+Tax
GTX 460 may cost less
I would rather not not buy anything than buying HD 7750~HD 5750
BTW My resolution is 1600 x 900 on a super LG LED Monitor 8M:1 DFC