It hasnt got HDMI.
It is capable of recieving and displaying high definition content.There are several ways of connecting High Definition devices.
Hdmi is one
DVI is one
HDMI carries audio and picture
DVI caries picture only and is more used for LCD computer displays.
Both are digital and show an identical digital picture.
In this case its different as the DVI socket Dream Multimedia have put on the DM800 has been modified to output sound over DVI aswell as video.
So just because something has HDMI doesnt mean it is gona show high definition pictures.
All you would need is a DVI to HDMI cable.
As for is it worth getting,thats up to you.Its gona cost about 350 pounds and there isnt that much HD content or channels.
Seeing as I dont think you understand what HD is I would say no.