On the Gen II's (I know it's a 2000) an awesome idea would be to take out the spare, cut a hole in the spare compartment cover. Put plexiglass in the hole and put a 15" sub in it. Just my opinion and if spares weren't important I'd do it.
I have had a bandpass, and although it was loud and low the sq was not that great and the bass hits were not accurate. I went to a sealed box and although it is not quite as boomy, the sq and accuracy of the subs more than make up for it.
for audiobahn subs i would still go with around 2 cubes sealed. that oughta give you a decent Q, depends on which model. i would suggest a bigger box if you have the room, but 2 cubes should do ya right.