Too see what the benefit may be, it's best you understand what actually happens when you connect digitally. Put simply, you end up using the electronics in the Avant to decode the sound, rather than the DVD1's electronics.
The digital output is effectively a 'direct data output' from the DVD disc itself. Connect this into your Avant, and it will decode the sound information instead.
The Avant's sound processing will be of a hugely superior quality to that in the DVD1, and when using for example, Pentas, BeoLab 1s, 3s etc... the difference may be large. Then again, many people are lucky enough to not be able to hear the difference! I wouldn't expect the difference with Avant speakers to be massive (as stunning as the speakers are).