I've used N320 quite a bit in .40 and somewhat in 9mm. I had gone to N330 in 9mm to get a little more velocity.
N320 is a fairly fast pistol powder. According to
Hodgdon, it is very similar to AA#2. SSK has published info that #2 is not appropriate for a gas operated gun in .300 Whisper. However, in a manually-operated gun, it should be just fine.
In my limited testing, AA#2 did seem quieter than loads with similar velocities using a slower powder like AA#9 or H110. This makes sense, as the faster powders will produce less gas volume for the silencer to have to contain.