Most newer and better quality subs play down in the low 20hz range and some even go lower than that, they really add more rumble and shake for HT. Yours would be good for music with the lower point in the spec at 35hz. The EP350 specs out at 27hz and in room is sually in the low 20s. My PB13 Ultra reached down to 15hz in my room - generally anything below 20hz is considered subsonic - you don't hear but you feel it. So with your current sub you are missing out on at least 15hz worth of sound and even more feel.
All subs will sound overpowering when turned up beyond the mains output level, this is why an SPL meter is required. It will allow you to veryify you are not running the sub hot(higher than the rest of the system). As Randy noted the newer avr's have setup programs that set the system very close to even on all channels, but most seem to still have problems setting up the sub woofer correctly and certainly not to the liking of everyone using it, as some just like more bass than others.
The question is how does your sub sound with the rest of the system? I thought my old sub sounded pretty good until I started down the path of no return when I started demoing subs, then I realized just how much I was missing
