A cap is definitely not the solution to this one, as mentioned above, try turning down your gains and all that stuff on the deck then see if they sound better, then raise levels slowly until you're as happy as your going to get with the quality Vs. Quantity thing.......could be the box too, check manufacturers specs compared to what the box really is and see how much difference there is....a bag of poly fill in a box thats too small can turn from sounding like ass to bliss (smells bad when you blow them up however)