Welcome to the forum! This is a good place to spend time researching your upgrade.
I would suggest connecting with fellow forum members in Kolkata to get an idea what different systems sound like. As you spend more time in this hobby your ears will start "resolving" audio differently as you learn how to spot different aspects of sound quality. An example of this is bass - typically many like to have a lot of bass in their music at first. For me personally I now have learnt that this is not real and prefer much more natural sounding bass. Your tastes will vary so take some time to find out what you like first.
Keep an eye on the "For Sale" section of this forum. It's a great place to get good deals from forum members who care about music. When you feel you are ready to make a decision you can always post on here for others opinions which will help you evaluate your decision.