Newb said it best. And caps are useless to a SPL burper. They drain too fast and then load the system. For transient music that an SQ-oriented system is more likely to play, they can help out in those passages where the bass comes along quickly and goes by quickly. Like a bass drum hit as Joe said. I've personally heard the difference to a bass signal when a cap drained. It was on a song with long tones and you could hear when the cap drained and the amp clipped as the voltage dropped.

To listen to a system that has no cap and then listen to another car that does and to say "Oh your bass doesn't sound as defined. Must be because you have no cap" is a pretty bold thing to say since 1000 things could be making that bass sloppy. I use a 1F cap and I feel better knowing I have it.