Remove Fan from CPU Cooler?

[Namrednals]

I'm currently modifying a Power Mac G5 case to house a new hackintosh build I'm working on, and have decided to use the original cooling methods used by Apple back in the day.
 
The original G5 was cooled by 2x front 92mm intakes and 2x 92mm exhausts out the back (see pic below). They all ran at varying speeds depending on the load the CPU was under. (FYI the G5's were notorious for running hot. The fact Apple couldn't get a G5 running in a laptop was why they made the switch to Intel in 2006).
My G5: http://i.imgur.com/Hwiov9J.jpg
 
My current CPU cooler in my current mini-ITX system is a Zalman CNPS5X: http://i2.rozetka.ua/goods/8369/record_8369011.jpg
 
It's cheap, but it does the job of cooling my Core i5 4570S well, with the fan installed on the front and with the aid of a rear 120mm exhaust (@5V).

 

My plan is to rip the fan off of my Zalman so just the heatsink remains, then replace the original G5 fans with 4 Arctic F9 fans, and then run them all at 5V.

 

Would that be enough to cool my 4570S? Or should I invest in a beefier passive cooler like a Zalman FX70?

 

Thanks guys.

[LogicalDrm]

Its really hard to say just like that. What kind of temps under heavy use you are getting now? It looks like the fan is connected by plastic clips. So if you are careful, you can take it off and put back on. Like do testing on test bench style before installing it into case.

[Stefan1024]

I think the CNPS5X will have a hard time to keep the 65 watt CPU cool without a fan. The heat sink finns are close, so you need some static pressure to push the air through.

The FX70 will be much better (and more expensive).