Which audio driver for the Gigabyte Z270X GAMING K5?

Solution
BOTH.

The chip is from REALTEK so you need the Realtek drivers, however the Creative software works with the same chip as well.

"The Sound Blaster X-Fi MB solution provides premium audio quality, effects and features for PC systems equipped with only basic onboard audio..."
If you have an external sound card, then download the correct drivers for it. Realtek is the proprietary soundcard "in" your motherboard and not external. From what I can remember, you should not need to download audio drivers when purchasing a new motherboard...?
 

This is what is shown in the specification page:

1 - Realtek® ALC1220 codec
2 - TI Burr Brown® NE5532P operational amplifier
3 - Support for Sound Blaster X-Fi MB5
4 - High Definition Audio
5 - 2/4/5.1/7.1-channel
6 - Support for S/PDIF Out

And this is what is shown in the Key Features page:

http://i.imgur.com/S4ikjvo.png

It's not very clear which ones I'm supposed to be using, since I'm nbot using any external sound card.
 
BOTH.

The chip is from REALTEK so you need the Realtek drivers, however the Creative software works with the same chip as well.

"The Sound Blaster X-Fi MB solution provides premium audio quality, effects and features for PC systems equipped with only basic onboard audio..."
 
Solution

Thank you, so I'll have to download "Realtek HD Audio Driver (Note) Improve ADC to 114dB SNR" and "Creative SB X-Fi driver" and leave the older "Realtek HD Audio Driver" alone?
 


That is my understanding.

I'm not clear on WHERE the Creative software is used. I have setup Audigy for a few older games though, but even though they offer it I'm not clear what the benefit would be without actual X-Fi hardware. Probably does SOMETHING or else why include it?

Looking at the LINK you gave, when dropping down to the X-Fi MB reference it appears that this software is the INTERFACE for Surround, "VoiceFX", and a number of other settings, and the Realtek solution is what you'd normally get (with a program interface, but it also contains the basic DRIVERS for the audio chip).

Probably there will be some crossover with functionality but you'll figure it out.