I have owned this Sony 12” sub for 3 years now. And while overall I am happy with it for the price, it gets too boomy at higher volume levels. To compensate for this I usually need to turn down the level on the sub. But I have read on audio review that adding some polyfill to the box can help to tighten up the bass to an extent. Is this worth doing? Will I notice a difference and will it really make the bass less sloppy at higher volume levels? If it does make a difference I guess the only thing that would keep me from doing it would be the fact that I still have a year left on my service plan from best buy. And doing the mod may void that warranty. Thanks in advance for any input on this.