Theres a few but i don't see them using capacitors.
Any issues with "auto shutdown" running on the pc psu? what is your amperage rating on that?
I did that for a bit, but at peak (split second) the subs would pull 25+ amp. Under-powering them would cause the amp to shutdown for a couple seconds then kick back in and resume the beats. I ended up buying a dedicated variable voltage psu with peak amp of 30 and it seems to correct it.
2 12" L7 solobarics w/2KW amp at 2ohm. It was quite impressive though. It put most high end subwoofers to shame for the price.
You desperately need a inline Capacitor if your going to make it work flawlessly with a high power amp at sustainable volumes for any amount of time..... The larger the capacitor the more Thunder strikes the subwoofer can pull out of the capacitor before the amp drains it all and the power supply starts delivering the amperage itself and obviously the PSU your using needs to exceed the peak amperage draw of the amplifier itself in case that happens.
You also need to Use a power supply with a single +12v "rail" or line... whatever the term is, You can't use PSU's with the dual or triple or more +12v rails... Just the single rail ones (they'll provide all the amperage from a single source....and bridging those +12v lines isn't something i think you can physically do anyways?)
But the capacitor is the secret key to the whole set up working.