When using "straight through" DVI switching, as the 990 does, there is no issue with the alledged "Blacker than Black" issue.

Based on what Microsoft said in May at E3, and more importantly what they did NOT say or show, the Xbox 360 will probably NOT have BluRay or HD-DVD. Current betting is that unless they make a last minute course correction, the HD playback for movies will be in the "WMV-HD" format only. Microsoft has been VERY close about what the actual connections on Xbox 360 will be, and it is worth noting that NONE of the units shown either at their press conference or on the E3 show floor were positioned in such a way as to allow anyone to see the rear panel. Insiders indicate that the current plan still seems to point towars analog Y/Pr/Pb connections via a "dongle" similar to what the current Xbox uses and that there will be NO HDMI on the 360.

You shouldn't have any problems in using the 990 with the DVI-HDMI cables.