Well, a low quality (IMO) woofer in a generic bandpass box is going to sound...well....like shit.
I hate to say it, but first
most bandpass boxes (see bass, I put that in there just for you

) sound like shit to begin with. Couple that with the fact that these woofers are designed for small sealed enclosures, and you have a recipe for disaster with a generic bandpass....sorry to use the word generic and assume that's what you want to do...but that's what most BP boxes are.
If the budget is really that tight, I would suggest going sealed and sacrificing some output. You may also want to look around for some used equipment. Your $$ can go a lot further that way.
Any bandpass box will be fairly large...if you care more about $$ then you do trunk space, go to adireaudio.com and buy one Shiva. Sure it looks very plain jane, and the box requirements are big, but it will be a step up from most any sub with "Sony" on the dustcap.
What is your budget BTW?