Okay thanks. So far the only thing that will do it for me is PowerDVD and only when playing ISOs mounted as virtual drives. That's good enough for me but I was curious what others found.
On my system Boxee and PowerDVD play the non-HD DTS 5.1 tracks from an MKV but not the DTS-HD MA tracks. As an experiment I ripped (with MakeMKV) two videos with only the DTS-HD tracks and both Boxee and Media Monkey 4 (beta) hung. With a normal MKV rip PowerDVD only sees the 2.0 and DTS 5.1 but not the DTS-HD tracks. With mounted ISOs PowerDVD sees DTS-HD MA and plays it fine with a nice DTS-HD Master Audio banner showing on my receiver. The experimentation continues.