Serious bass needs serious woofers. I was thinking about the original question of which brand/model to recommend and to make it simple i would start by choosing among the well respected brands to help apply a coarse filter to your choice. My brand choices would start with Alpine, MB Quart, Hertz, JL Audio and Rockford Fosgate. (These are just some of the brands i am biased torwards)

Then get into the specifics of their best offerings using datasheet and specifications to narrow down further. Then the hard bit, you have to listen to them but here is where you are faced with car audio shops which sometimes make the process difficult. Ultimately, the old adage is mostly true...you get what you pay for so expect to shell out cash for quality.