Loud equals pissing off people who have trails going through their property which in some cases leads to them closing down the trail to the clubs & local government that run and maintain said trails. Also it can also cause issues with decibel noise levels laws with w/e you call the DNR regardless if you only go mountain riding as well. Better off with clutching then doing a can.
Pretty hard to find after market for those sleds and I really doubt you will. I've seen people just take off the muffler and put a pipe. Louder, but the bigger thing was weight. That muffler on there weighs about 12-15 lbs. Yeah, heavy for a box. Saw one guy with a 583 put a muffler from a 4 wheeler in there. It stayed quiet and it saved him about 7-8 lbs.
Quiet cans I see no issues with as those are mainly for weight savings as you said. Loud ones however cause nothing but issues for everyone on the trails, dnr and homeowners with trails going through their property. And stay away from cheapo chinese garbage if you are even able to find something. Unless someone is racing I don't see the need for them or pipes for what 1-2mph? Better off sticking that money into clutching or just saying eff it and buy a bigger motor.