Ok. It is like this. I have Rocsford Fostage CD/MP3 player. I have a Rocsford Fostage AMP and it is 400W 200M. In side speakers are SOny, and Pioneer. Now is the question which sub to get. Few choises right here please help me decide.
1.) Audiobahn AW1251T
2.) Alpine SWE-1241
3.) Rockford Fosgate Punch HE2 RFP3212
4.) MTX Thunder 6000
5.) MTX Thunder 8000

So thats it. It is going to be a 12" sub. Powerd by the amp ROCKFORD FOSGATE 200M

is the alpine a type, R, e, or *? out of those subs there i dotn see much that would be "pushed" by 400 watts off the top of my head.... i would say go w/ a kicker Solobaric L5 but im just partial to them

Try a Bose fulcrum analyzer in series with a Pioneer 4-phase variable turbothruster.
If you get static or blow speakers, try kicking up the juice to the flux capacitor. I suggest 4.6 Gigawatts.

to be honest with ya pick the cheapest one...that amp will not push out that much so it should all sound pretty close to the same...it really depends on what kind of $$$ u want to spend...look at gettin an amp upgrade...i got the rockford 351M and Rockford 10" he2s and i dont think it pushes out enough so...

Check out Adire Shivas. They're low on the price range, and they sound like they cost twice as much. There only limiting factor is that they like a bit more air than others (bigger box).
I've got 2 of them and You can't touch them for sound per dollar, period.

Shivas are Nice!!!! Get whatever amp sounds good. You'd be surprised what you'll need. And fosgate amps are very underrated too. A nice 12" HE would be fine. I personally LOVE the HX2s...

My polk audio sub being pushed by a "180w" JBL amp was VERY Loud compared to many 500w+systems. It'* all about setup, and yes it was in a bandpass box.