I need to repalce my subwoofers. I've got up to $1000 including box materials to spend. I already have an amp I don't want to replace, 500wx2 into 4-ohms, or 1000x 8ohm mono. I'm thinking about a pair of Ave 15 drivers in the recommended 2.2cu ft boxes. Maybe buy a BFD if I need to help <30Hz. Any opinions?