Your board may not run smoothly by mixing ram. I recommend you sell your 8 gb corsair ram and get a 2x8 gb kit for around $85-87 (current pricing newegg). But don't expect a big performance improvement; it all depends on what you use your system for. I downgraded from 16 gb to 8 gb and didn't notice much difference.
by the way newegg do not supply ram in India, is there any other who supplies ram to India with manufacture's warranty.