There are PCI fans available. I'm not sure on the layout of the Quicksilver, but you could pick up a PCI fan to cool the components more directly (bad English, sorry).

They are relatively cheap. Or you could go all out and throw in a water cooling system. There's a review of one in the hardware section. It was pretty sweet. I'd make sure to measure the top of the machine before getting one though, as the 733 I tested it on was just a 1/2 inch to short to sit evenly on top.