Oh yes, that would work. But I also have a surround sound receiver, and lol I have filled it with hdmi cables, so the xbox is stuck with component :P
I'm sure your receiver has an Optical S/PDIF port on it and you can use both the HDMI and Optical Audio cable at the same time. But its your choice if you want to use the lower quality cables. There's no difference between the HDMI and Optical Audio cable
in terms of sound quality. Both can easily do Dolby Digital 5.1 and that's the best the Xbox 360 can output.