I know what you mean... The trend is to use a "competition only" model (motocross race bike) that are only tuned to meet AMA noise requirements which are aimed at closed course racing. These bikes are the highest horsepower models available, and make the best snow bikes for that fact. But then a lot of fellas purchase aftermarket exhaust that is even louder. Why? I have no idea... The performance gains are minuscule compared to the annoyance factor. There are options out there that reduce noise, but they come at a cost - usually a loss in performance.
My solution was to buy a bike that was already reasonably quiet and leave the exhaust alone. My riding buddies say that unless they are directly behind me while really chugging up a hill, they can't really hear the motor.
As stated above, the Husky 501 (and it's orange twin, the KTM 500) are excellent choices. They make great power without being overly loud. I went with the Yamaha WR450 because of reliability and I have a great dealership. I'm a smaller guy, so that bike makes sufficient power for my needs.
One more point that should be made... It is common for these bikes to be held in the higher RPM ranges for long periods of time, versus the on-off throttle of their intended use. That really exaggerates the noise level that they produce. I've been an equipment operator my whole adult life and also am prone to migraine headaches, so I wear earplugs a lot. It is common for me to wear them when vacuuming the house because I am sensitive to the noise. I wore them when I raced motocross even in the 2 stroke era. I carry them in my pack when riding the snow bike in case the noise starts getting to me, but have only put them in a few times. And it's mostly due to the noise from other bikes - not my own. Just something to consider...