You should definitely use what is available on your case. eg place a fan at every single fan grill on your case. The pci card coolers do work, but you only need them if your cards are getting really hot, which they most likely aren't going to.
you can tap power from any yellow wire and ground on the wire next to it. i use machine screws to hold my fans in place. and if noise is a concern or you want to do some overclocking then water cooling would be a good option. the prices have come down to the point where it is possible to put together a good system for around 100 bux. good luck whichever way you go