Alright, I've been stumping myself for a couple weeks now on my new build, trying to plan this out ahead of time. Well the time has come and I still haven't decided what would be best.
I know this may be confusing, but hopefully the pictures I add in at the bottom, will show what I am talking about. There are 3 120mm fan slots at the top, 1 200mm and 1 120mm in the front, 2 120mm on the door, 2 120mm on the lower hardrive bays, and 1 140mm in the rear, and 1 120mm on the interior side of the mid-level hardrive bays. The case has many fans, and I've switched out the stock fans with my own preference for the time being. I've also decided to go with a single loop liquid cooling, so the Corsair H100i took the job.
My problem is: I have all the fan slots filled and most are intakes. I have the radiator as an intake with 2 fans on top of the radiator to push cool air in and 2 low profile fans underneath it to pull air out of it, helping to keep the cool air moving. The front is intake, the two side fans are intake (they blow on the graphics card and motherboard), the mid-level interior fan behind the hardrive bays is a secondary intake, plus the two 120mm lower hardrive bay fans as intake; and lastly, the rear is exhaust. This CANT be good? I have how many fans as intake and only 1 140mm as exhaust. Im assuming pressure is going to be pretty big.
Okay, first off, I think you are way over thinking this. Pressure isn't going to be "huge"; the case simply isn't going to "store" air. It will find it's way out. And if it can't, the fans won't suck in any more.
With that said, you have way more fans then you need. The fans on the rad are fine. The exhaust fan in the back is fine. The front fan is good, blowing on the HDD. The two fans on the side are useless, get rid of them. Actually, they are probably raising your temps, if anything; the GPU is trying to blow the air out and you are blowing that hot air right back in on them. Get rid of those and leave the vent open. As for the motherboard, it already has four fans from the rad blowing on it so it is fine. The fan in back of the hard drive is doing absolutely nothing so get rid of that. The lower two fans, unless you have HDDs down there, get rid of them as they aren't doing anything either. Scratch that, get rid of them anyways; if you do have HDDs down there, move them up.
That should leave you with the 2*2 fans on top for the rad and MB, the one fan in the front for the HDD, and the one exhaust fan in the back.