Thanks for your replies....
in regards to gain setting, my HU is 6v so the gain is already set low , maybe 1/4 full or less (used DMM to set)
i just had to ask this question because most articles recommend to match amp power with rms rating of sub(or close to it). So I was never sure if I was hearing close to the full potential of this sub. It only really comes alive when close to full volume, but I assume this is normal, at least with sealed boxes.