As u already have 4GB DDRII now why not invest in a E7500~5k or Q8300 ~ 6.8k and O.C sightly. You might check out themarket deals. There are few E7400 proccies on sale. I dont see a dramatic increase in performce spending 12k on platform change + 2.5-3k for RAM change ( difference after selling existing RAM).
Alternately u can also try to O.C the E5200 to 3.5GHz - 3.8GHz
The E5xxx series has good O.C potential.
Edit: Just saw u dont prefer to O.C. Missed that.
Q8300 performance is on par with Athlon II X4 635. The Higher clock of E7500 also will come in handy in most of today's games. So just do a small proccy upgrade and do an entire overhaul when required.
If u are having issues with the mobo too and want an upgrade then i would say go the AMD way. Its better VFM with your budget.
Components Description Price (INR)
Processor AMD Phenom II X2 555BE 4900
Motherboard Gigabyte MA-785GMT-USB3 / Asus M4A88TD M EVO/USB3 5600/6500
The Gigabyte one is a AM3 mobo with USB 3.0 whereas the Asus offers SATAIII ports too. Go with the Phenom II X2 555BE if you are ready to gamble on unlocking (~80% success). Even if you cant unlock, its still a potent enough proccy for your gaming.