The post with the Dell SLIC seems to be for board rev. 1.0 , do you have a new rev 2.0 board? It has updated sound and network, not sure if they use same BIOS (but they might very well do). I'll be getting my GA-P55-USB3 board in a couple of days, I'm not sure what rev. I'll get.
I tried it an my mother board did not like it. I got a MD5 on that file of 613298f3e0020f8f3ee530fa0e5b8ce8. The flash failed. I have flashed 4 machines so far and all have gone well but this one. I will try flashing back to the factory version.