It can really depend on the case as to the number of fans you need.

Just a bit more of info.

Do you have ribbons and cables in the airflow path from the front case fan to the rear ones? If so get them out of it.

Check the cfm of your fan on the hsf. the higher the better.

I have used the Volcano 9 here. By the way, I like looks of the Volcano 11
But I am at presently using the Cooler Master Aero 7 which is quieter and no increase of temperatures. Think I'll stick with it.

Front fan blowing in, rear fans blowing out.

And make sure the ribbons are out of the airflow path.
Here are some examples


This diagram should give you a general IDEA of how the air should flow through the case.

I use Artic Silver paste and the Thermal compound instructions are here.

So, i have the front fan blowing in and 2 in the rear blowing out plus the one in the power supply.