Cooling Heatsink Fan: Suck or Blow?

I am going to install a Silverstone NT06 Evolution while I faff around with this project http://forums.bit-tech.net/showthread.php?t=287561

So should the fan blow or suck? I do have a 120mm extract fan very close to the heatsink.

 

Thanks.

 

If you can have one doing each, then even better.

 

Given the cooler that is not an option.

 

Yeah, I know, I was just being lewd.

 

Ahh.

 

I've found that generally sucking air up away from motherboard gives better results.

Reason is often when blowing down the air hits mobo, turns out hitting RAM, GPU, etc. turns up along side of cooler & fan and gets sucked back into fan before it is drawn out of case. But if air is being pulled out of cooler the heated air is drawn on out of case without mixing with airflow over motherboard to cooler.

It's not always true, but then the only rule that can't be broken is that there is an exception to every rule.