My 6 year old Sony only has an Optical Out. Are you guys sure the Coaxial Audio Out is passing 5.1 Audio? My Sony down converts it to 2 Channel on the Optical. Maybe newer sets allow this.
My tv is an RCA 48" flat panel, about a year old. It has the option to pass through "raw" uncompressed audio. So in answer to your question, yes, I am getting true 5.1 audio through the coaxial output. The TV is just passing through the audio from the HDMI cable.