I also have the Samsung HD-931, and use the DVI port and upscaling (in my case I prefer to upscale to 1080i rather than 720p).

The results are excellent, and I find the picture far superior to the one I get through the component port. This is not a valid comparison however, because the upscaling and highest quality output features available with the Faroudja chipset on the Samsung are only available through the DVI port.

The only major complaint I have with the Samsung is the quality of the audio decoding. This problem goes away of course when you pass the digital signal straight through and use the DACs in the 990.

I am using the Hitachi 65XWX20B as my video display unit.