The only way that dvd-a/sacd cd outputs in digital is if you have a high end player with firewire outputs and a high end receiver with firewire inputs. But if you take a dvd-a and put it into a regular dvd player, it will output in dolby or dts, so you will still get surround sound, just not as high resolution as dvd-a/sacd. This will only work with dvd-a though, sacd's will only play in a sacd compatable player.
Josh is correct - apart from the newer firewire or HDMI connections DVD-A only outputs via the analogue channels same as SACD. Through the digital outputs you would only get the DD or DTS version of the recording.