Did you use speaker-level inputs? Self-amplified or external amp? Clarity inside car?

Sorry I've got so many questions, but I'm trying to rectify the inadequate bass problem with my Concert stereo, and I already have 2 older SAS bazookas. They're 6" non-amplified tubes, and I'm trying to decide how to proceed from here. The amp I used to power them in my other car is out, so I'm trying to decide whether I should buy an amp to drive these tubes, buy self-amplified tubes, buy a different sub, or do nothing and be satisfied.

Thanks for all the help!

I did have a 8" w/ a built in amp, but it recently was drowned. It did a great job, but I was not looking for a massive amount of thump. I just wanted to increase the richness of the sound. It could handle what I wanted and probably could have stood a little more damage. Power is not what toasted it, water damage was. Oh well moving on to a 10" bandpass. The only reason for not going back to a bazooka ,is that I had this lying around from another car I use to own.