|Dude, most of us know that your country uses 230v power. That is useless info & has nothing to do with the discussion about power supplies / SMPS.|
Do NOT buy a SMPS from a "concerned shop keeper". All he's concerned about is putting your rupees in his pocket. He is going to try to sell you crap - iBall, iCute, Hytec, PowerSafe, VIP, etc. - these are all low end garbage units that will give you nothing but problems. Order your computer parts (decent quality, brand name) from an online vendor & have them shipped to you. You need to buy a reputable brand like Antec, Corsair, CoolerMaster, Thermaltake, etc. And quality costs money, so be prepared to pay a lot more rupees for something decent.
Other than that, you didn't address my questions. What is the make/model of your current SMPS? What is the wattage? How many amps are on the +12v rail?