The standard customs duty used to 29.6% but now due to GST, the customs duty is 10% basic customs and IGST @28% since amplifiers fall in the 28% GST product group thereby making it a total of approx. 41% on the value declared...
On top of that, all electronics need to be BIS certified and because you cannot get 1 amplifier tested for BIS (which also costs money and a very long time), you will end up paying money to the customs/agent to release the product as well as demurrage... My speakers were held up for almost 12 days even though it does not come under electronics but I still ended up paying demurrage for 10 days even though it was the customs fault for holding the product...
I have always imported stuff directly in the last 15 years but would advise you against it as recently it has become very difficult and expensive unless you are getting a very good deal on the amplifier... I only recommend importing large speakers directly now as the difference in the Indian pricing would still be worth it.. For all other products, either fly down and carry them yourself or bargain with the Indian distributor/retailer...