Wow, has it really been this long since I posted here? I intended to return and update before now.
My efforts to create a duct system failed- the little Dimension 3000 case simply doesn't afford enough space to accomplish what I envisioned.
In addition to the roof-mounted fan, I ended up going with a CPU cooler and fan and a newly installed 120mm fan in the front of the case. I considered ducting the CPU fan to the side panel but, from past experience, knew it would raise the noise level and decided against it. My new theory is that filling the case with fresh air from the front, forcing it across the CPU and exhausting it out the top would provide sufficient cooling. I found a couple Panaflo 92mm fans at Frozen CPU for 99¢ each, so I bought them in the event I needed additional air flow from the back. I've not needed them.
Those evil little bastard gremlins that reside in my "Black Hole" computer have a large family. Many of its members live under the hood of my truck. Be cautious not to piss me off, for I will give them your