Verified answer

dude,,unless you can afford something like a kicker warhorse( $10,000) or rockford tk15 ($25,000) your gonna need 4 separate amps. Fi btl hit 2000 watts rms so your gonna have to match that. It also depends what ohm you decide to go to either 1ohm or 2 ohms, i say go with the two because you can wire that down to a 1 ohm and get 2000 watts off a 1ohm stable amp

Dont waste ur money on the BTL, get some RD audio Heavy Weights. They are more designed for SPL applications, and for a little bit of money, you can add a flat wind coil on it which ups the wattage a good 500RMS per sub. They can also handle massave power burps. A friend of mine did a wall job in his 2000 Hyundai Elantra. Put 4 of the RD HW 18s in it lol. Its SUPER LOUD. As for the amp thing, they have RD amps that match, or look for a goos amp such as the Rockford T4k. 2of those would handle 4 18s pretty well.

Dude. You're gonna need around 50,000$ just to run that system. You're gonna need multiple alternators and over 5 batteries. Just check this guy out.

This guy has the loudest SUV with 4 18" Fi BTL.

http://www.stevemeadedesigns.com/index.php?option=...

Notice how he has a 20 cubic foot box, 7 batteries, four 350 amp alternators, FOUR 4000 watt RMS amps which are around 2000$

Good Luck with that system

Rockford Fosgate Tk15

fi btl is with the help of far a harder hitting sub 2000 watts rms and the t2 is purely 1000 rms and the t2 value alot extra!! however the t2 will sound extra efficient so far as squaregoes!! yet purely like everybody has stated the field determines how deep and loud you bass is!

either 4 rockford fosgate t2000bd's.... 2 rockford fosgate t4000bd's or 1 rockford fosgate t15kw