More on sync:

A lot here depends on your source. If you are using the set's internal tuner you may still have delay depending on whether or not you are watching a native HD source (OTA or via a direct QAM cable connection with the CableCard) or something that is upscaled either at the station, or within the set when used with an external SD or analog source. Add a DVR, external cable or satellite box, or any other source, and there is more than a fair chance that transmission path issues, upscaling in the Samsung or any one of another few issues will throw the sound and image out of sync. I've heard that older Samsung models did induce a fair amount of delay because of the scaling/processing they used.

THAT is why, DVI, HDMI or anything else aside, you'll want to run the audio into something such as a 990 that has lip sync delay, and as noted by His Supreme Gonkness, set it individually for each input on the 990. HDMI ain't gonna help you there -- if you use the tuner in the TV, you wouldn't want to run HDMI back to the 990 ANYWAY. As you correctly note, an optical or coax cable is best for that AND BESIDES, that lets you have an analog back-up as well.