I wasn't aware that the 2910 had firewire (though the 3910 and 5910 do). I'm pretty sure that it doesn't have D-Link, which is Denon's proprietary scheme allowing both DVD-A and SA-CD to travel digitally to an appropriate receiver or processor. But if I'm wrong, and you have the right ancillary equipment, then you can eliminate the bundle of six analog cables previously necessary to carry these formats and presumably get access to improved bass-management capability in the process. Some people who use D-Link say that they notice an improvement in sound quality; theoretically, the elimination of noisy interference could be a factor, though any meaningful differences are more likely to be hardware-dependent. But the main advantages would be superior cable and bass management. The optical or coaxial digital outputs can't handle DVD-A or SA-CD because they do not incorporate any copy protection. Regular PCM, DD, or DTS would not sound any better via HDMI or firewire than via optical or SPDIF.
Edit: I should also mention that eventually HDMI will be carrying SA-CD and DVD-A, and so far as consumer audio is concerned, this development is much more meaningful than anything that individual manufacturers do with proprietary firewire encoding, since HDMI is a universal format.