The monster rounds aren't going to be "quiet" after you remove the cat. Your original mufflers are going to be louder without the cat as well.

 

Dresser duals are not the way to go. They are for show, not go.
Also don't wste your money on any HD tuner but instead buy a PC-V and install it yourself. It takes less than 10 minutes. Fuel Moto will also sell you a killer intake along with the PC-V. It will come right from them with the map you need all loaded in it.
As for the stock slip ons maybe but probably not. It's all about flow. You can try some of the Vance and Hines slip ons that have an optional quiet baffle and go that route.
That way when you get bored with all that quiet you can take them out and unleash the beast.