Max and all the others--question re: case vent strategy

I live in sunny California and it can get pretty dang hot in this room certain times of the year. My ambient temp in here was 85F today, and as a result me PC began making me reduce it down to stock speed, which I am loath to do.Here's my plan. I'm going to begin building me next PC soon and I plan to purchase a case (not sure if aluminum makes sense in this situation) and modify it accordingly:1. tape up all ventilation holes except for the one in the back and high up that is typically the exhaust vent hole.2. cut a hole most probably in the bottom, or perhaps the side and towards the front, and connect this hole with a professional flexible ducting to a 4-6" duct that will go under my subfloor of my house. This should not cost a whole lot of $$. I want the end of the intake duct to be close to existing ground so that air is sucked up into the case from under my house. I measured the temp down there during the hottest part of the day today, where it was 94F outside, and it was a balmy 69F under the house near the ground. The crawl space is actually about 4 feet at that point.3. then I will glue a first class collar, prob from PVC or ABS plastic plumbing fitting, around the exhaust port up high and in the back of my case. 4. I will then mount a wall fan, of ultra low noise, remote from the PC, such that when the fan runs there *should* be hardly any noise. I am searching for a lower rpm, adjustable fan to do the job.The end result will be . . .1. Connectors on the PC, and on my floor and wall, that allow ducting to carry cooler air from under the house into the PC and out of the room. The main reason for putting the exhaust fan exterior to the PC is to get rid of the noise. I would really like this next rig to run very very quietly.Now, here's the question: does anyone know what kinds of power in a fan system in CFM or whatever I should need to overcome the static resistance in approximately 15 feet of 5-6" ducting? I really would like a fan that is fully speed adjustable, yet super quiet. I should be able to mount the exhaust fan motor under the subfloor yet through the perimeter foundation so that it truly is remote from this room is my goal.Would it be important to have fan powering the intake side as well? Anyway, sounds like alot of hassle but I think it would operate very inexpensively, be not too much to buy parts for, and most of all would improve the case ventilation significantly while not being noisy. And of course in the cool months the sucker will be downright COLD inside!!Your thoughts are appreciated.Noel