Can I use a Thunderbolt to HDMI cord to output audio from my iMac?

I'd like to run audio from my iMac into my stereo receiver in this way, but I'm not sure if it's possible. I was hoping to find out if this was a viable option before I bought the cord.

Bonus question: is a thunderbolt to HDMI cable going to be a higher quality audio setup, as opposed to running a 3.5mm audio cable from the iMac to the stereo?

Thanks in advance for your help!