I had to do the same issues with mine. I was installing mine on a mirrrored drive config, so I had to have the drivers for my SIIG card.
I installed the OS via a USB stick and also added the SIIG x64 drivers on the USB stick as well. I was able to browse to the driver and everything was good. If you you are installing from a DVD you still be able to have the driver you need on a USB stick
and be able to browse to it.
I hope this helps.