Why do I get the feeling you are looking for that elusive chest slam/punch sound so many like from the bar/dance scene. This area of sound is in the 50-80hz range and it is produced mostly from your mains as it is generally in the roll off area of the crossover points. I could get a ton of punch when I ran the M80s with the A1400, no sub required.

Jumping up to the 18" driver just lowers the tuning point and gives better low end response, IMO.

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70