How do you make your exhaust quieter?

[aerosam]

I've noticed that my exhausts are way too loud, so I have to make it considerably quieter.

I'd rather not add a second silencer to each side as it would look pants, but I will if that's what it takes. I'd rather fit inserts inside the pipe, but won't that sap some engine power? And how effective are they really?

It's a question of this:

https://www.jetex.co.uk/jetex/store/...productId=2769

or one of these:

https://www.jetex.co.uk/jetex/store/...productId=2772