I'm not convinced with Sony's S-Master digital amplifier myself as their first generation of digital amplifiers had shown the need for improvement.
However, I've heard that those things are capable of delivering a fantastic sound when you play a purely digital signal through it. Plus, it's very possible (and perhaps even likely) that Sony has perfected its digital amplifier in their second generation models, which is what the STR-DA3100ES is.
If you're curious, go ahead and audition it! Who knows, it may be what you are looking for. Plus, Sony ES has some of the greatest warranties you can find if you ever need to use it. - Reinhart