The Volt 15" is nice and so is the ATC SB100-375SC but a pair of either of these woofers will set you back close to $1500, which you can use up to around 500 Hz....so you are looking at a costly speaker.
The TC Sounds LMS 18" Ultra at around $1500 for one unit is another serious driver.
The TC Sounds LMS 18" Ultra at around $1500 for one unit is another serious driver.