[crjdriver]

Are you using a fan controller or what? I highly doubt a single motherboard fan header is able to supply all of the pw for 6 case fans.
If you are using a fan controller, then the speed would be controlled through that OR the controller will plug into the fan header on the board.

 

[crjdriver]

Why would you want the fans running at max speed? That is going to be quite loud.
Here is what I would do. You have 3 fan headers on that board and a pump header [most bios will allow you to config the pump header as a fan header] I would use 3 or 4 fans and connect them to the motherboard. You will now have control of the fans either in the bios or from the asus software.

FWIW I am not a big fan of fan controllers. Every case I have used with one, it remains disconnected.

 

[crjdriver]

6 case fans running at max speed has to sound like a hair dryer.