I don't really think sound is a manufacturer's consideration when talking exhaust. I haven't even ridden my new Strat, just bought it and won't get from dealer until Spring. I have heard the Strat has a nice sound/tone from factory, but I am sure I will be changing the exhaust anyhow. I am leaning towards the Freedom Exhaust True Duals. From info they sent me they designed the exhaust for stock tuning and on the bike with what they call "step" technology to replicate the correct back pressure for max torque. Believe what you read?? In this case, probably, but don't care, the look of the exhaust is awesome (to me)!! And from videos I have found on YouTube the sound is a mellow rumble and not ear shattering loud.
Dealer recommends not installing duals until after first service (600 miles) that gives time for bike to break in and you know how it feels with the stock exhaust.