Every room, receiver, sub, and position, will result in different results. It is not normal that you would have to put your sub gain on maximum, unless you have the receiver truned way down, but even then seems unlikely.
Do you have one of the newer 350's? If so, they are much more powerful than the older 350's. I owned a 350 about 5 years ago, and the gain was about at 11 o'clock position. Then when calibrating all the speakers to around 75dB, that placedthe receiver around 0dB level for the sub channel.
Have you calibrated everything with a Radio Shack SPL meter or built in receiver mic? Are you bypassing the crossover on the sub, and just using the receiver crossover settings? Do you have the other speakers set to "small" with and 80hz crossover?
Also, keep in mind with music you won't hear that lowww boom boom compared to good movies with low LFE, unless you liten to RAP.
Placement is also very important.
