omg guys!! check this out:
I prefer my audio gear look sleek and elegant, not hardcore and uber leet. I can see a controller looking alright with a camo skin, but not a headphone amplifier.
While the mixamp needs a 5.1 DD source to work correctly, it's Dolby Headphone output is only 2 channels (which is why it works with your stereo headphones). The surround sound effect comes from the HRTF cues that are processed into the sound.
So RCA cables are perfectly fine.