I suspected to have the same problem and tried to use the orginal firmware, but
failed to do so. I did not try to excract my "own" firmware but tried to use
the firmware from the zip file that was attached by Jordan as we have the same
card (both GTX 660).

But if I boot with the nouveau.config="NvGrUseFw=1" kernel option, the kernel
stops directly on the attemp to load the nouveau fb driver.

I must mention that I use UEFI boot and my kernel resides on the EFI partion
(/dev/sda1) at /boot/EFI/Boot/gentoo/bzImage-3.12.5.efi (the mount point is
/boot). On the other hand my firmware is at /lib/firmware/nouveau/ on partition
/dev/sda5, which is mounted at /.

Let me guess: I need an initrd file in order to make it work? :-( Then I must
figure out how to make this work together with UEFI boot. Until now, I tried to
avoid initrd and UEFI.