Stick to the Realtek onboard you have. Those Supreme FX cards aren't really sound cards, they are more like an audio riser card as the motherboards that come with them have no audio built in/on the motherboard.
As far as it working on a motherboard other than the one it came with, I honestly have no idea as I have never looked into it. If you do want to try it then you will have to find one out which of the Asus boards it came with and then get the ADI/Soundmax driver
directly from Asus.