Dear Navas,
Videocon HD Zapper box provides Dolby Digital 5.1 output through Coaxial Output.
It means you should have a receiver or home theatre which should have Coaxial Input.
I personally uses Sony HT-DDW990 Digital Receiver for HD Sound from Set Up Box.
HT-DDW990 - Sony Black Component Home Theater System at Abt
And quality of HD sound is awesome....
So buy a home theatre with Coaxial Input and enjoy it.