I would say 9 times out of 10, they are fine, and I have more then ample amounts of bass... Moderate to high listening levels... they are fantastic.
But as annunaki has also stated, in that 25hz and below, I am asking more from thos subs at extreme or ref. levels that they start to cough...
When I play music, this is totally a non issue... but for those movies that troll really low and I have them tuned to 16hz, playing at ref levels they just don't have enough... they rumble things in my house plenty, they shake and scare people that are not used to it, but I am really aware of their capabilities and for me its not enough... I want more...
More power, more control, cleaner deeper bass...
Remember that my room is open to many other areas of the house... stairs up to the bedrooms, open to the dining room, and to the kitchen.... It is not sealed. So maybe I should say my room is more like 20,000 cu ft. and they won't cut it...