If money is not an option I would purchase the bass engine from a pair of the Scaena loudspeakers, they are 3 stacked per side 18 inch woofers in a specially designed cabinet.
They go, low, low, low, fast and articulate with massive pressurization. Check out HP soundings review of the Scaeana's
There is no substitution for massive displacement of six 18 inch bass drivers and a few thousand watts of juice!