For the Indian market, the seasonics are typically the best option. I think you can find the 520w version of the S12II for around 4-5k RS
Is seasonics S12II 520w efficient for r9 270x??
Yes, the r9 270x has a max power consumption of around 250w (20 amps) and your cpu (guessing either an fx or i3/i5) won't pull more than 130w (11 amps) so the 520w S12II (with 40 amps on the 12v rail) would be able to handle it without averaging more than 80% of the rated power. You typically want to run your PSU at 80% or less for efficiency.
Note that the 250w consumption is for torture testing, with gaming you would see something more like 200w usage from the GPU.
Edit: woops lookd at some wrong numbers, the 270x would consume around 150w max not 250w max, average gaming usage around 125w. Was looking at the r9 280x numbers before.