2 ohms or 4 ohms?

 I just bought a jeep cherokee and I'm working on putting a sound system in it. I'm going to go with 4 Tpye R 12s in the back. I'm going to purchase 2 Alpine MRD-M500 mono class D amps to push the 4 subs. But I don't know what model of Type R to get to match that amp specs. I can either go with the SWR-1241D (4 + 4 ohms) or the SWR-1221D (2 + 2 ohms) subs. Which model subs should I go with to match the amps? Also has anybody hooked a cherokee up and knows what it takes to get it pushin some mad bass. I want to hit in the 156 db range is that possible with this Alpine equipnment? The head unit is going to be a poineer 7000 high output.  I haven't bought anything yet so I can still change things around.

Either sub impedence will work with this amp.  I assume you are planning to connect two subs to each amp?  You'll want to wire for 2-ohm total load no matter which type you get.  After you deside, we can tell yo how to wire them.

You want to hit 156db, eh?  You compete at idBl?  What class?

Go with a MRD-M1001, and 4 SWR-1241d  it will be about $200 cheeper and you will get the same amount of power to the subs.

If your going for a loud  spl system that also sounds good during normal listening, i found that tuneing around 50hz is the best.  They still sound musical, yet hit extreemly hard.  I have worked with the techs at Alpine to figure this out.  Be shure to separate each sub in its own chamber.

What model rockford amp would make these subs pound? Why should I make sure they all have there on sealed box? Is Type R still the best sub to run in there?