if you're willing to get the dyno tune you could try installing some sort of baffle in the exhaust, and then get the bike retuned. You may lose some top end but if done right gain some bottom end (also depends on the style of the baffle).
This is guaranteed to quiet down the bike, and there are many options on the market, even custom made is an option. I built a custom baffle for my bike's RPW pipes which were too loud for my taste and now I love them. Everyone's tastes are different.
Most important thing is to match the outside diameter of the baffle to the inside diameter of the pipe section where you'd install the baffle. Do a google search for exhaust baffles and you'll find a lot.
2011 Victory Kingpin 8-Ball
Tach / Dual front discs with Vesrah JL pads / Penske shock / S&S Intake / PCV & autotune / RPW Thor exhaust with homemade custom baffle / Tsukayu leather "Strong" bags / Avon Cobra *Radials* / Ness Vegas Peg Conversion / Ness Vegas driver's seat / Custom T-Apes from BR Custom Cycles