I would advise waiting a month or two I have a C1, and it's not particularly useful right now as the software support is not really 'all the way there.' You basically have to use Hardkernel's official linux or android images if you want modestly functional hardware acceleration, and the device isn't really useful as a media player without hardware acceleration. I've got a little R-Pi that would be cool to get MC on to. That all being said, I enjoy reading about what's next and it's a positive that the devs get a prod every now and then. The first 2 have video capability which was a pleasant surprise that it came around so soon. Given the development these guys have been pushing over the last year or so, they're going great guns rolling out Mac, Linux, the Id, Pono (work in progress). You'll be a person of value because you'll (hopefully) be at the forefront helping with user feedback.

There's one thing I am sure of though, if/when an ARM build is ready for release it will be mostly functional and you'll know about it. And I've noted that Jim and the JRiver crew prefer to undersell themselves and then deliver the goods to a timeplan that they have confidence in. Then Hendrik said he was having a dabble.

An R-Pi version was first mooted on Interact (that I recall anyway) back in July:

Jriver media center raspberry pi 3