Vance and Hines slip-on 16777 sounds great. A little deep and not real loud. Reqiures no A/C or download. Better than factory. Have one for sale. 120 plus shipping. Has about 200 hundred miles on it. Went to 2 into 2 for looks. wish it sounded like the slip-on. If interested PM me.
Whatever you think what sounds best for you. Go listen to some pipes and make your own determination. I have bought pipes without listening to. $$ lost