I haven't read all of the posts, just kinda skimmed the first half, so sorry if this has already been said, but I think there are more ways than people think to watch youtube, movies, netflix, etc, over HDMI.
First of all, if you visit the atrix development subforum at XDA, you can find (either search, of just look on the first few pages), there is an HDMI mirroring app available. Of course, you'll want to make sure you . It's an easy solution, although imperfect as someone pointed out, but basically just make sure that you have your atrix in landscape orientation to watch videos. Remember, you're mirroring your atrix, so just watch videos like you would normally. I can't remember if this is just an .apk download (which would require root or use the sideload wonder machine... actually, doesn't the atrix allow sideloading now without any hacks? So perhaps VERY easy!
However, it might be a .zip file that you can install through clockwork mod, but not to fear; that is incredibly easy to do as well if you follow the instructions.
So that's sideloading, which I addressed because it's what you requested, but if it's videos you're after, there's an app (I can't remember what it's called, sorry!) that I believe is traditionally used with the media dock? It basically pops up a list when connected to HDMI that allow you to choose between photo gallery, videos, music, and maybe something else. It pops right up for me, and I always thought it did for everyone, but I guess it wouldn't surprise me if Moto locked that down too in order to bully people into paying what, like $50 bucks for the "media dock" aka "hunk of plastic with basic audio and video out interfaces."
If you're reticent to root your phone or do anything not sanctioned by Motorola (not making fun of you; your phone is expensive and the thought of "bricking" it can be rather intimidating, so if you read all the directions for something but still feel unsure of yourself, I guess listen to your gut... remember, it IS 100% legal to do whatever you want to YOUR phone, though), then you may have to dig a little deeper, but I'm nearly positive that at LEAST basic mirroring is possible to achieve without rooting or anything too crazy. Check out XDA, just don't post in the development threads, and search before starting a new thread; they take that stuff pretty seriously over there!
Good luck!