^ if u need to add dust filters and then add extra fans, to get "increased ventilation" then it shows there is fundamental flow in the Cabinet design itself.
Also adding all these 3,000 worth fans is crazyness.
If one FAN(on backside) fails to do the job for your Cabinet then even 4 fans won't do it. Problem is with the Cabinet design, not fans.
I have noticed that Cabinet sellers are purposefully keeping things so much cramped & squeezed that users end up buying fans to keep this khichadi cool(due to lack of poor space given by designers). If Cabinets are built 1 inch wider, you can safely eliminate 1 FAN (3000 Rupees).
I bought my old Pentium 12 years back and i remember that my Cabinet was same size that these Cooler brand type guys are selling today. So basically, they did no improvization in design and are forcing the users to spend extra to rectify flaw with extra FANs.
Also, you won't notice any performance difference even if you overclocked a processor by 20% because only 10% of this amount(20%) is actually utilized by gaming software.
10% of 20% is 2 percent. So, u spend 3,000 extra to fans, then overclock processor. And you end up with 2% improvement.
Added Later: I also noticed one thing: FAN sizes are deliberately kept big so they eat space inside Cabinet, which adds to ventilation cause. Heck, those fans i saw are bigger in size than FAN in my bathroom window(such small fan does job perfectly for big bathroom. That's what is called efficient design).
That's why branded stuff is better. Design flaws are minimum. In local market, u always end up spending more in the end for jugaad(with design flaws). Atleast this is what my experience says. Dell is making jobs of assemblers difficult now. Manual assembling is out of fashion now, except those who love "assembling" for the sake of it.