Totally agree with BlackCCT, it's all subjective to personal tastes and perceptions when it comes to loudness and perceived performance improvements. A Dyno tune will show a true performance improvement over stock. I've also read that you can take two identical bikes, put all the same modifications on them, Dyno it and still get slight differences between torque and horsepower gains from one bike to the next. Lloydz is a good source for seeing Dynos with various modifications.
I have a set CFR's (Carry Faas Racing) pipes on mine and I love the look and deep bassey rumble. They sound similar to Vance Hines, which I would personally go with if the dealer hadn't already put the CFR's on mine as an upgrade. CFR's are made in Peoria, AZ and take a while to get. Lots of options for sure, just got to look at and hear as many as possible and go for one. The stock ones were pretty lame when I was looking at bikes in 2014, so almost anything is an improvement.
I use the Victory 30 pin adapter with an iPod nano, or I use a 30pin to lighting adapter for the iPhone and run Spotify. Only problem with Spotify is I can switch between playlists, but you can change tracks with the thumb controls. So if you go that route pick a good playlist for the duration of your ride!
Oh yeah, there are several heavy debates on whether two into one or true duals are better and whether baffles or no baffles increase or decrease hp/tq. Good luck sorting through all that mess!