You're asking for something that's *just about* physically impossible from
5" speakers in imperfect enclosures (doors). Here's an experiment you might want to try, though. I have been told that Radio Shack sells a decibel meter that reasonably accurate. With the car's top off, and no Harley or 18 wheeler nearby to add noise, measure how many decibels of noise there are just driving down the road with the radio off. I think you'll find that it's pretty close to 100db, especially with the wind in certain directions relative to the car.To make enough clean, tight bass to overcome that noise if it existed in a bar, you'd want a lot more power than you have. You'd have larger speakers, and the enclosures would be designed for those speakers. I'm also a bass player, so don't debate this, OK?
By the way, what's the brand and model of your car amp?