if you have a power distribution block with 2 outputs you can connect the cap after the dist. block, you dont have to put the cap before it. take the first output and hook the cap to it and from the cap to the amp. and use the second one to hook up your second amp. hope that helped.
you should really just use one cap per amp as close to each amp as possible to be effective. you also should have 1Fd of capacitance per 1000 watts of power, and that won't replace the need for a beefed up charging system if you have dimming lights.