Yogesh, there are a number of problems in buying from outside India:
1. Voltage and plug issues
2. Some products are manufactured for specific regions. You will region and other issues with products such as DVD Players.
3. The product will NOT be supported in India by the local representative. Onkyo, Denon, Yamaha all specifically say the product will only be supported in country of purchase. Local distributors are so cheap that they will also not sign any annual maintenance contract after the first year is complete. International warranties have no value in India.
4. Customs is an unknown. You never know how they will react when you declare the products, You could get away scot free with no duty, you could be slapped some minor duties, or the products could be confiscated. Of course, of you know someone in customs, this problem could be solved.
5. If the total weight you are carrying is more than 20Kg, you could end up paying large sum for excess baggage. In addition, some airlines have restriction on number of packages you could check in. Singapore Airlines, for example does not allow more than 3 or 4 packages per passenger in addition to the weight limit.
Cheers