Airflow question on Cases with front door

Ok that might be a stupid question but I'll ask anyway.
I'm looking to buy a new system and I'm waiting for the Antec P180. Which bring a question. This case (and others) has an optionnal 120mm front intake fan. But then it also has a door that closes. I can only deduct than when the door is closed, the fan is useless as no air will be sucked through the door. So when you overclock, do you leave the door opened all the time? Wat is the impact on the ooling with a door closed? It has to be significant, right?

On my raidmax case (its like the chieftec dragon case), it has a door on the top, that uncovers 4 5 1/2" bays, and 2 3 1/2" bays... under that, its got 4 intake fans (80mms)... then theres a kind of plastic "grille" on the bezel... hard to explain, but it does allow air to go through

most cases are seemingly designed without airflow in mind at all, see nine out of ten stamped fan grills (blocking 50% or more of the airflow), no intake provisions, no vents for hot air from the vga card, etc.

i'm not a big fan of the p180's intake system. that said, it is a beautiful case and many people over at spcr are dying for it to come out.

I guess one solution is to leave the door opened or, if possible, remove it. Strange though that companies such as Antec who clearly target the enthusiast market do not think about that when they design...

AH, i see what they did... not goood.....

it intakes from the door hinge (see the little holes??)...

bad

hmmmmm yeah - bad