My Front L/R speakers have 2 8" woofers each, so they can handle bass just fine
It's a fair bet that
1) a good dedicated sub (or two) could produce more low bass output with less distortion than your towers
and
2) the towers are not in the acoustically optimal position in the room for best bass response
These are two good reasons why bass management -- i.e., setting loudpeakers to 'small' with an appropriate crossover -- is useful even when the front line are 'full range' speakers.