The Q9XXX core 2 quad processors were all better than the Q6600. See if you can find one of those.
I understand your situation completely, and I want to help you. When I lived abroad in a 3rd world country with no Amazon / ebay and much fewer options I procured my hardware (often used) through online gaming forums. Since even a generation old tech was expensive in stores, I found the best deals by looking for local PC gaming communities and forums online. I'm 100% sure India has quite a few things like that.
If you tell me which PSU you have and your budget, I can try and suggest some GPU options and maybe even help look for some.
You need to get some more DDR2 RAM. Get 8 gigs, keep in mind it may or may not work with your existing 4 GB (unmatched pair) but in my experience I have been able to get even different manufacturer's DDR2 RAM's to run together more often than not (always a risk though).