Supertrapps........?

Teighlor,
They can be a bit loud for the street...but not REAL loud. Depends on how many disks you use. Typically fewer disks mean less noise more torque. More disks mean more noise, more top end power.

Adapting them to OEM pipes can be a pain. Lots of different options.
JohnnyB

Teighlor,
If it's running nice and strong right now it's possible jetting could remain the same or more typically go up one size. On a 450 for street use I'd guess you'd start with about 5 4"disks on each side. Perhaps even four...these disks breath a lot more than you might think. 6 disks will start getting a bit loud.
When you install them, make sure the lips on the disks are facing the rear, and make sure you don't over tighten the screws and crush the disks together, that will close up the passages. Tight enough not to rattle and that's about it. Not a bad idea to drill and lock wire a few of the screws on each side even on a street bike.

Scott, do you have the "open" end caps or closed? Sometimes I think the open caps with disks are louder than straight pipes.
JohnnyB