As a general rule of thumb, I recommend 2 exhaust for every intake.
Now, I understand your need for GPU cooling, but theres really no point in pumping ambient temp air into a hot PC. You want active air on the GPU and hot air removal basically everywhere else.
I gotta admit man- you have one of the STRANGEST fan layouts Ive ever seen. If I had your PC heres what I would do:
1 fan in front set to intake
2 fans in rear set to exhaust
1 fan on top set to exhaust
2 GPU area fans set to intake (I guess... the second one is honestly pointless, and probably bad for airflow)
and that fan near the HDDs? Um... I spose I would set it to exhaust, but honestly dont see the point of that one either.
Is that sound card in the lowest available PCI slot? If not, move it as low as it can go.
To be totally honest, your cooling setup is kinda fubard in my book. People will probably disagree, but with all the odd placement of fans (2 side and the HDD one?) youre probably disrupting proper airflow and creating more holes than you need to.
System specs? Lets just get down to it people:
My penis is bigger than yours.