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(+) or (-) pressure

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Hi all I was wondering if there was any special benefit to having positive or negative air pressure in my case.

I was thinking if I had my case all sealed up except fo the fan holes and I had extra cfm's pumping in I could cut out a blow hole on the top of the case over the cd-rom's. Maybe that would work better than having just equal air flowing through the case plus I could possibly cool down the HDD and cd-rom's without buying one of these special fans (save room and money).

Then I was thinking if I had extra cfm's blowing out the vents in the bottom of the case would suck in fresh air. I don't know maybe that would also would work better that just the stata quo equal air flow.

If you have any thought's post and pls post if you've tryed some or all of those idea's.
That sounds very interesting I think I might try puting anywhere from 3-5 fans on the botem of my case and have them blow straight up and yet I will have the top piece of my case off... Heat rises so it might have some beifit... I hope =)
With so much airflow from fans inside a typical O/C's casing, natural convection (warm air rising, cold air descending) is virtually cancelled out.

With positive pressure, the dust will only collect right in front of the blowing fans while with negative pressure, air will be sucked-in through every nook and cranny of your casing and there's where the dust will be but otherwise the density of air wouldn't change so much as to impact its heat capacity.

I have a negative pressure case ventilation for convenience: one PSU fan and one drive bay cooler (at the uppermost bay), both blowing out -minimum modding of my case. But to 'encourage' air to take the correct entrance, I removed all the PCI slot covers of my case. But still, the negative pressure is so strong that it'll suck in small paper pieces. So far the dust problem is nominal.
I don't see as it matters as long as it's about equal. If you have enough air going through your case, it just going to pick up the heat and leave.

Course, you do have to make it flow...if you design it so you get eddies and whirlpools and the like, you'll probably be rather disappointed in your results.