This from Emotivas site: "The Differential Reference Modules in the XPA-DR2 are each made up of a perfectly symmetrical balanced pair of high-performance amplifier modules. Each individual amplifier module already has vanishingly low distortion but, by connecting them as a balanced differential pair, a significant portion of the tiny amount of remaining nonlinearity is cancelled out. As a result, we are able to achieve even lower levels of distortion in the XPA-DR2, resulting in remarkably transparent sound, with unprecedented smoothness and clarity."
I'm not an electrical engineer, so I'm not going to endeavor to add my own words... I read about it on Emotiva and other sites... all I can really say is that it gives you more power and lower distortion. That's overly simplistic.

I wasn't all that worried about the distortion, but I was looking at speakers that wanted lots of juice. I didn't get them, rather am enjoying the hell out of Philharmonic BMRs with Outlaw Model 2200 amps on each.
Is nice!
And I clear reference level peaks, even if I never push it that far. But I can.