You want a fast sub preferably multi driver for accurate pitch.Magnepan say's if your going to use one don't go over 6" on each driver single or multiple.REL is one or MJ Acoustics from a group of former REL employee's who went off on their own.Another choice is martin Logan who are as you might expect with a ELS going to be accurate though people who I have heard from who have used both say ML actually is suited from HT as much as REL and at a certain $$$ point in both lines REL is more musical ML more slam.But neither are "boom in the room" HT products and if your looking for a less expensive option than Vandersteen 2WQ is another multi driver music sub.REL Storm. would be bit more.if you want most bass than Martin Logan Depth i.All have bass producing surface area of larger subs but with multiple drivers they are faster and more pitch accurate.Add a Velodyne SMS-1 EQ to any and you get their benefits plus the room correction found on Velodyne and other traditional "bigger is better" subs.I am trying to get friend to add a Depth to his 3.6's.
Chazz
Chazz