@ blaisecardoz
You didn't say if your engine was fuel injected but as this is in the UCE area of the forum I'll assume it is.
If your bike is a US import it will have a oxygen sensor (O2)in the exhaust pipe right in front of the cylinder. If this exists, any replacement exhaust pipe will need to also have a port for this sensor.
If your motorcycle is in India it will not have this sensor so any exhaust pipe that is made for the 500cc Royal Enfield engine should work.
The Electronic Control Unit for the US bikes uses the O2 sensor to check the fuel mixture and it will accommodate some of the silencers which have some restriction inside of them.
It doesn't seem to like the straight thru silencers and if one is used, a number of backfires will be heard indicating the air/fuel mixture is too lean.
Like barenekd says, noise does not always mean power. In fact, I know a number of people in India who found they had lost low end power by replacing their factory stock silencer with some very loud ones. Many of them switched back to the original when they found this was happening. When they switched back, the old power returned.