Hi Vishal,
i will suggest u to go for Antec 300 /350 or 450watt. you can get it easily from your nearby dealers.
And for technical help i am giving you a link i think it will help u to know more about PSU
Power Supply 101: A Reference Of Specifications : Power Supplies
Dear dont you think that 7yrs warranty is too.If because of such a big warranty u are paying more its better go for 5 years warranty you can save mone also. Brands u can choose seasonic/ cooler master/Antec or corsair.