if you wont to wake the neighbors up early in the morning its perfect :) I had it installed in a matter of mins. the BG quiet core is on its way ill see if it will tone it down to keep the cops away from the house..
It is hard to say specifically which exhaust system for your bike would be the loudest. Big Gun Exhausts are known for a deep, loud tone. This muffler would be significantly louder than your stock muffler.
This will vary based on what you have done to your TRX450, such as intake kits or ignition, or even a cam. On a stock motor with correct jetting jetting you can expect a peak increase of about 3-4 horsepower and also the same number for torque. Keep in mind you will need to jet accordingly for the exhaust. This is considered a bottom to mid exhaust so it will hit harder down low and through the mid without a huge increase in power in the over-rev portion of the rpm range.