Don't use the Realtek driver. Use the X-Fi drivers. You pay for superior audio, use it and find out for yourself. You may need to disable Realtek in your bios.
I don't know anyone who would pay a premium for a MB such as yours to let that X-Fi chip go to waste.
FYI don't listen to anyone who don't use a dedicated audio card. They can't speak for the audio quality. I have a X-fi Titanium Pro Card which is the add in equivalent to Supreme III audio chip on your board and it kicks onboard Realtek to the curb.
A clan member just installed a X-fi Xtreme audio card in his rig. That card is actually far inferior to mine but still above realtek by a touch.
And the X-fi utilities are actually using the Supreme III chip, Creative will never let Realtek use their software. Realtek wouldn't be able to Run EAX and Tru Studio Pro anyhow. So Soundblaster X-Fi is more than just a Utility.
I suggest you find a site like Overclock.net who should have a Rampage Formula IV club, and chat with people who actually can clarify a lot more than someone who doesn't own the board.
***EDIT***
Want help, from users of this board go here:
[Official] ASUS ROG Rampage IV X79 Owner's Club