idq's o a seal box will give you a very nice and smooth respond and they can still get very loud and maintain they natural sound and probably that is your problem . you might want a more bassy respond like a ported box.
you mention that you lack of room ,even had problems with the idq's verily fitting , so a ported box with eights might work or even the idq's if you can make a ported box for them.
i would still prefer the idq's in a seal box for better result of bass respond , but that's just me