I would recommend getting a larger sub with more displacment, a BTL 18" would have no problem beating out lows while tuned to 40hz, my MT 18" kicked out lows while tuned to 42hz. and so did my TiPro 15" once you have enough displacment the sub will move enough air to the point where it doesn't matter if it's tuned to 40hz... I've done it a few times, but smaller subs won't agree with that. I have a 9510F and it doesn't believe me when I tell her she can play low tuned to 40hz... displacment is key for that imo some people will say you need to tune low, but they probably didn't have the same experiences I did with larger subs...