It looks to me as if you have a pretty simple situation, actually - I'd run HDMI-to-DVI for the HD DVR and the OPPO 981HD, and stay component with the XBox360. If Microsoft adds HDMI to the 360, you could shift to component for the HD DVR - component will handle 720p and 1080i just fine, and I've found that at least with my HD cable box the picture quality is identical via DVI or component.

While we're on the subject of the XBox 360 and HDMI, I've got a question that might be pretty relevent to this discussion. How will they be adding HDMI to the XBox360? That's a hardware change. The only way I see to add it would be to revise the platform and start selling an "XBox 361" (similar to the way Sony did with the PS and PS2 to reduce their physical size).

Using a player like the Oppo's that has an HDMI output provides a digital signal path for your DVD video all the way from disc to display - just because the source material (DVD) isn't HD, that shouldn't make it less worthy of such a connection.