A couple of sub questions.

[shotokan_teen 0]

I am looking at doing a blowthrough in my truck (yeah I know...its going to be expensive and a lot of work.) I'm not sure on the subs I want to run yet though.

I'm looking at either 2 BTL's or 2 RD audio Alpha V.2.

The sizes I'm looking at are either 18s or 15s. I want it to be loud at low hertz but I also want it to HIT hard and not just be loud with no punch to the bass. I have 4 Crossfire VR-1000D amps (putting out probably right at 4000 watts but will be more with the Big 3 and more batterys).

which would fit what i'm looking for better?

[shotokan_teen 0]

anyone?

[Aaron Clinton 2,372]

I cannot comment on the other driver, but I know the BTL is a ground pounding monster. You have to have the power and the box for it. If you strap a pair of amps per BTL, you should be fine. I have not been around an 18" BTL yet, but I know they have been a big hit with people who own them.