After considerably research, I have decided to go with a "positive pressure" system, so I'm going to have more fans blowing in than exhausting. I did the Head Case thing and ordered seven more fans, in 120mm, 140mm and 180mm sizes. They won't be here until next week, so I've finished a temporary build with the 3 fans that came with the case and one on the GPU cooler.
Crappy photos to follow:
Yes, the GPU cool is a little bit cockeyed. I fiddled with it until I concluded that "better is the enemy of good" and I should stop futzing around. The wiring is very messy and quite temporary. I'll do a proper wiring job when I've installed the pile of fans I ordered.
I have yet to power on the system. I'm pausing to make dinner right now and I, uh, need to find my Winders 8 install media.