Depends what you are looking for. If you just want loud bass then pretty much any brand will do. If you want precision and accuracy (clarity) then IMHO JL Audio wins hands down. I have listened to top of the line Rockford Fosgate, Infiniti, MTX, Pheonix Gold, Alpine, Soundstream and not a single one of them can match the clarity of my entry level JL Audio W0 subs. I listen to alot of music that demands accuracy (ie multiple bass drum punches) and my W0s hit every single punch just as if they were coming from the actual drum while the brands listed above stumbled though them like someone falling down the stairs. The other thing I notice is that other subs produce an annoying sort of distorted "fuzz" that can be heard even at lower volumes.
You really have to crank the JLs before you hear that sort of sound. Anyways IMHO, if you just want loud bass then go for MTX, Alpine, ect. If you want an accurate sub that isn't going to cost you $800-$1,000 then definitely go with JL. Kicker traditionally has also been very accurate however, I have heard that in recent years that thier quality has dropped off.
