I think its kinda funny how everyone says capacitors don't do shit. I guess I don't know if it works as well in cars as it does in home audio, but I can tell you for sure they are absolutely necessary for dynamic music in a home theater setting. It stores up all of that energy so it can release it during extra loud notes so the speakers will kick harder. I think if set up properly a capacitor is a huge benefit.
Take for instance my larger HT amp which has 8 massive capacitors, over the 4 smaller ones on my smaller HT amp. It sounds MUCH more dynamic because of the added power it can store.