Sorry, but the difference is inaudible. 1536Kbps DTS core cannot be separated from DTS-Master. Also view this for all silliness regarding 192/24:
http://xiph.org/video/vid2.shtml
The most important benefit of the HD format is that they take effort to produce a good soundtrack, with good voice separation for the center channel, and don't do the ugly dynamic range compression that appears in so many pop CD's.
Especially if you don't have a huge decent center speaker, complaining about the stream being no HD is totally nonsense. Having a decent center speaker still is the most valuable in your HTPC setup.