Case fan placement

i have 4 cases fans and a 3rd party cpu cooler that has one fan but can add another which i might later and which works wonders for me.Just keep it like on top of your desk like i do with enough room for it to blow the air out of the case. You can add more if you want to though, I see nothing wrong with it. I can still add another 4 fans to my case if i liked since i have a big case and has good ventilation with holes on the top of the case and the bottom with a see through case with led fans that blow out through the wholes on the left side. Anyways up to you if you want more fans then I believe it's alright. Just make sure there blowing the air out and not in because once i accidentally put the fan backwards once :P and it made my graphic card hotter then i realized it was backwards and set it back to how it was suppose to be and made the temperatures go down lol, just my piece of advice make sure you put them in correctly they have little arrows on them indicating which way they spin and blow.

Inigma,
With only one hard drive and one GPU you should be fine with four. That being said there is nothing wrong with making sure the case has good air flow. The layout of the air flow of your case is similar to mine but I have twin front mounted fans and four fans in push pull on top flowing through my H100 corsair. A side intake fan and standard rear exhaust, PSU and two 50mm rear case fans tops it out. Oh don't forget the GPU fans on my card. It's very important to consider super quiet fans or fan controllers or both when running lots of fans.

I've always opted for lots of fans for my cases but I always got the loud ones. It really is worth extra money and effort to get some super quiet fans because under load you can really hear it.

Are you running a stock CPU cooler? The stock intel ones will actually push air onto your ram, motherboard etc and itd be better to get your hands on some arctic silver 5 thermal paste and a decent cooler. (The 212 is a nice budget cooler I'm opting for the noctua d14 on my next build. This would be a better upgrade if you don't already have an aftermarket cooler. Also considering case size a guy at work put his antec 1200 system into his antec 300 and got better temps due to its size. There can be a lot of 'dead' air circulation in the case. But yeah, I would probably personally get a fifth but replace all of them with fans that have lower noise. I'm buying a corsair 600t and the stock fans are atrocious so I'll be up for some quiet fans soon. I would say majority of the fan spaces are worthwhile, as its been said already if 5 degrees makes a difference to you personally then go for it.

what you can do if you get another fan, and flip the ones on top and make them intake. i had the same for the longest time, and thought about doing it . so 1 in the front, 2 on top, and the one on the side, leaving the one in the back as exhaust. i forget what kind of pressure it makes and it helps prevent dust from entering your case. it also keeps your components cooler since you got 3 fans pointing and shooting.

If for what ever reason loud fans don't bother you go for it. The same for quiet fan, if you like them do it. Quiet fans do cost more. But I'm worth it.