Are rear fans necessary? [Corsair 250D case]

[ClownWalker]

Hello people of the interwebs. So here's the thing, I'm building a new pc in the next months or so and I'm questions about the cooling:

1. My case will be a Corsair Obisidian 250D Mini-ITX.
Intake :
- one 140 or 200mm fan at the front
- two 120mm fan on one side
Outake :
- gpu fan on the other side
- two 80mm fan at the back
So, should I use the rear fans for better outake?

2. My case will be a Corsair Obisidian 250D Mini-ITX. So the motherboard is facing up and there's no outake on top, only in the back and the sides. Since I'm not overclocking, water cooling is not to be concerned. But what about aftermarket fans and heatsinks? Should I use a vertical heatsink such as the Coolermaster Hyper 212, so that it blows out the back or should I keep my stock cpu fan that will blow on top, where there's no outake?

I hope I'm being clear and specific enough!
Thank you for your time!

 

[clutchc]

Stock heatsyncs don't blow out the top of the case. They force air down/over the processor. Same with the fan on the gfx card; it will force air across the card's heatsync. Not out the side of the case (unless by turbulence).
You don't NEED an exhaust fan. If you have enough intake fans, exhaust will take care of itself. For that case, I would try it as it is. It sounds like you have enough fans. That case is a fairly new design and may work well. Corsair is not know for making junk.

 

[ClownWalker]

Stock heatsyncs don't blow out the top of the case. They force air down/over the processor. Same with the fan on the gfx card; it will force air across the card's heatsync. Not out the side of the case (unless by turbulence).
You don't NEED an exhaust fan. If you have enough intake fans, exhaust will take care of itself. For that case, I would try it as it is. It sounds like you have enough fans. That case is a fairly new design and may work well. Corsair is not know for making junk.

Thank you for clearing that out for me. I will use the fans as mention by Corsair.