but what about the hot air from the graphics card, (easily my hottest component befroe I put a fan on it) and what about heat from the ram?
I don't think a PCI slot has enough space for a large throughput of air. though a flexible tube is a good idea, I've only ever seen heatpipes molded in plastic that output air thought the small grates above the keyboard/mouse/usb etc cable bits.
perhaps a telescopic design and encourage people to cut a hole in the side of their case, that way you can accomodate different depths.
the fan should low out of the case drawing air from the inside of the case througfh the cooling fans then out of the case.
(this would be easiest to make, but fans are much more efficient at blownig that they are at sucking.)
Without extra cooling the air there is no way that the air can be made colder than the ambiant temperature it's only the movement of air accross the skin and the effects of evaporation etc that makes a breeze seem cool.