Street bass is fine, but your still not going to be happy with the small improvement for the money your spending. Most drivers around the same size / price, will sound pretty similar. You can put the same driver in very different enclosures though and get a very different sound.
Small drivers 12'' ect, aren't going to get you anywhere is a large car unless they are very high quality, the ones your looking at aren't.
This is what i am reccomending -
IST Mach 5 IXL-18.2.2 18 Subwoofer [IXL-18.2.2] - $319.00 : Infrasonic it is good enough on it's own that you can just simply put it in a large sealed enclosure. Or you can build the sort of enclosure for it that will move everyone around you, it's up to you.
It's within your budget but you need to be willing to look outside the square, because it's a brand you haven't heard of, doesn't come from a car audio store, and none of your mates have one. You'll also have to be willing to take someone elses advice and follow it to a T.