For my dad's 60th this year I told him I'd buy him some slip ons for his bike. He purchased it new in 2003 and hasn't done anything to it. Since it sounds like a sewing machine instead of a Harley I figured it was about time to upgrade him. That said, he has no idea what he wants (I figured he'd know) so now it's my job to find something that works. I know it's a very vague question, but am looking for help.

What would you recommend ? He's 60 so not trying to set off a bunch of car alarms, but want it to be "loud"... ya' know ? I've heard $2-300 is a reasonable price for slip ons..... is that correct ? PLEASE help me....