You would have a port for each woofer... you could have multiple ports for each woofer depending on the design.
Bandpass boxes are very difficult to create to custom tailor the sound..generally pre-fab bandpass boxes wont be made specifically to your woofer's specs.

I recommend the sealed box and a good woofer. What's your price range? or are you sticking with your xplods for now?

Bandpass:
(# of ports are all for design and what freq. to be tuned to... so dont assume you need "x" number of ports for "x" number of woofers)




Ported:
http://www.thezeb.com/images/brands/...ubzoneZbox.jpg

Sealed:
http://www.thezeb.com/images/brands/subzone/HJ121.jpg

Boxes come in all sorts of shapes.. some have plexi windows to show off the magnet/driver...

Prefab boxes like Subzone......Q logic... sealed.. will be your best bet.. find out the woofer's volume requirements and match that up to the box's volume..