That's pretty clever, putting a video source in so that the connection is established for the purpose of sending audio through the TV speakers.
As for your question, I don't know of another way to just feed audio into the television. It doesn't have an auxiliary audio input - like most receivers would have - so the way you have it - tricking the television - sounds like the only way to run it.
I have a Samsung LN40B550 LCD TV, with it's slew of inputs. For one of those inputs (AV2 for instance), I'd like to have a Sirius radio as the input to be able to use the external speakers that the TV is using.
I'm able to 'steal' video from another source and hook up the audio from the Sirius and hear it while watching the other source, but I'm not able to just use the audio by itself (I try to switch to that source and it says there's nothing there).
Anyone know of a way to get this setup to work?