Best place to find capacitors?

Truthfully, until I got into car audio, I'd never heard of a 1F capacitor, really all you need for about 500W would be about 50000uF, but to be save we'll say 100000uf, when I hear 1F about 10x what you need for a 1000w it's laughable, get an aftermarket alternator.  That bogus rule of thumb won't dissapoint, but a .5F should be more than enough.