yes the quiet core will make a good difference in the sound, you will not have to rejet with it .
whats the point of putting the pipe on there if u are not going to rejet and u want it to be quiet.....?
shoulda just stayed with the stock pipe
fyi: if you start it up in ur garage it is MUCH louder than it is out on the trails. i really dont think its too loud at all. HMF on a grizz or the aaen pipe on the polaris are louder