Pioneer sucks, Rockford is decent, Kenwood is decent, MTX is good, Coustic is good, JL is good, Alpine is good, Diamond is Great, Xtant is Great, MBQuart is Awesome, Focal is Awesome...
It all comes down to your budget, you can spend anywhere from $30/sub to $3000/sub for 12s...what can you afford.
P.S. Don't forget that your subs need to be carefully matched to an amp or a set of amps and wiring and possibly a sound processor...just food for thought.
You also shouldn't forget that it all comes down to your ears...Opinions are great, but you should really try to listen to as many different speakers as you can. Personally, I wouldn't put a JL sub in my car, not because they're bad quality, but because I just don't care for them that much. Others would swear by them. If you go listen to a $100 sub, and a $400 one, and you personally can't tell the difference, there's no reason to spend the extra money.
I just picked up a Infinity 120.3dvc sub and powered it with a rockford fosgate 451s bridged and i cant possibly imagine needing more bass in my car ('00 gt).. it sounds great, hits really clean, and when i want the thunderous bass it's there for the taking.
Like Joker said, it's up to you, really. We can only give opinions. That said, on top of what others said, Image Dynamics, Resonant Engineering and Adire Audio make great subs.
I understand it is up to what I think is good. I have personally only used JL products. I currently have a 10w7 and I am looking to get rid of it so I can have 2 12's again. I used to have 2 12w6's and JL is basically all I have ever used. I am just trying to figure out what people think hits harder. I am using the JL 500/1 amp by the way. Anyway so you would say MBQuart subs or Focal subs? Anything else? I need something that will hit hard with that amp.
if you want something that HITS and you don't care all that much about sound quality the top of the line MTX Subs (the Thunder 9500 series) will hit like hell...but I think you need to pump more than 500 watts RMS to keep them happy...I have a buddy that is running two of them (12s) on 3000 wats RMS and they bend 14 gauge sheet metal (no bull****).
Off of the JL 500/1 you are going to get about the same bass out of 2 W7-12s as you will out of a top of the line Sub from any other company...If you like JL stick with them...if you are looking for a top of the line system then you should look into more amps and more power and heavier amps.
ive heard diamonds, they sound horible. u want bass, get a pair of infinity perfects i got a pair of those, and the amps only putting out half power and i can hardly hear my self think with those.
well too heavy for a stang but I have owned Phoenix gold amps and the only other brand I have heard that hit just as hard were PPI.
if you are looking for a good amp now I would recomend the Xtant 1001 (1000 watts 1 channel) or the PG Octane 30:1 (3000 watt phoenix gold 2 channel amp) for serious subs like strokers.
try searching the net for class D amplifiers. but only get amps for the power you need to get some nice clear sound. and the best subs for bass are JL W 6 or 7s... just my 2 cent.
take a look at elemental designs, adire audio, resonanant engineering, image dynamics. As for mb quart and focal, i haven't heard too much out of their subs. Their components are top of the line no doubt, but their subs, eh idk.
It all depends on how much you want to spend. Honestly if you got the money, go with a pair of brahmas and throw a good 1000 clean watts at em, and you have sa VERY clean, yet VERY loud system
If you want quality go with Phoenix Gold or Xtant...if you are looking to get a high power amp for a lower price like you were mentioning you could get a 1000 watt RMS mono Earthquake Amp
Ya I have actually already decided on just 1 Brahma 12" sub, but im looking into amps. Has anyone heard anything about Hifonics amps? The Xtant and Pheonix gold were a little outta my price range. Im lookin to spend somewhere around the $300 - $400 range, for the amp.