Capacitors : Do they work?

NO!

There is a long drawn out explanation that can prove why capacitors don't work the way that most people expect them to, but unfortunately I think it would be too boring for most of you to read let alone have me type it all out, so I'll attempt to give you some quick advice on why you should not buy a capacitor.

Why doesn't it work ?

The best sound systems are ones that are powered properly. A capacitor does not work to fix underpowered systems, it merely puts a bandaid on the problem. The best advice I can give is that if you are running a sound system with under 1,000 watts, a capacitor might help you in the smallest of ways. If you are running a sound system with 2,000+ watts, a capacitor is merely becoming a hinderance. Either way, the money spent on them will not give you the results that money spent on a new alternator will get you.

To gain the ultimate edge and power your subs even during the peak of bass hits I would reccomend getting a high output alternator and then doing the big 3 upgrade.