With four 12" drivers and "not enough bass"....I'm very suspicious of the room.
Even though you don't have a subwoofer....do the subwoofer crawl around the room, on your hands and knees, sometimes moving your head up and down and see if there is good bass ANYWHERE in the room. If so, then speaker positioning vs listening position adjustment will be critical. If not, then you just might have one of those room that has so many cancellation modes that these speakers just aren't going to work in your room.