Newbie Question - Video and Audio Monitoring

I'm new to the post end of things, so please forgive my ignorance.
I've ordered a Blackmagic Cinema Camera and plan to shoot, edit, and mix some of my own narrative work.
If I'm posting on the new 2012 iMacs that include an TB to HDMI out, do I still require a converter or studio monitor like the mini-monitor or the HDlink? I can't find anything on the BM website that clearly articulates why these devices are needed.
In other words, can I not simply feed a video signal out from FCP X or Premier Pro to my Panasonic plasma over HDMI without a go between interface? What does the interface do to the signal?
Can I also not send a 5.1 audio signal out over HDMI directly into my Onkyo THX 7.1 AV receiver in order to monitor a 5.1 mix out of Logic or Adobe Audition?
If an interface is in fact required, what would be the best Blackmagic product for facilitating the output of both an HD video signal to a plasma TV and audio signals to an Onkyo receiver for 5.1 monitoring?
Thank you.
*Edit: "TB to HDMI out"
I've ordered a Blackmagic Cinema Camera and plan to shoot, edit, and mix some of my own narrative work.
If I'm posting on the new 2012 iMacs that include an TB to HDMI out, do I still require a converter or studio monitor like the mini-monitor or the HDlink? I can't find anything on the BM website that clearly articulates why these devices are needed.
In other words, can I not simply feed a video signal out from FCP X or Premier Pro to my Panasonic plasma over HDMI without a go between interface? What does the interface do to the signal?
Can I also not send a 5.1 audio signal out over HDMI directly into my Onkyo THX 7.1 AV receiver in order to monitor a 5.1 mix out of Logic or Adobe Audition?
If an interface is in fact required, what would be the best Blackmagic product for facilitating the output of both an HD video signal to a plasma TV and audio signals to an Onkyo receiver for 5.1 monitoring?
Thank you.
*Edit: "TB to HDMI out"