Which kick basses for my doorboards

Hi, I got doorboards for my car the other day. The boards have space for 3x 16 speakers per side. Now my question, which kick basses are what? (priced, if possible cheap!) What does this look like with the crossover? Do I need a 3-way? Then we would be at the power stage. Would there be a 2-channel, which brings about 350-400W RMS, that’s enough? PS: For the bass there are 2 Eton Crag Woofer. 2×30 (600W) to Audio System F2-500.