It sounded like David Sterne to me, too. Excellent voice actor, and he does a large variety of villain voices in DA2 that sound different from each other. Among the people he's done are Magistrate Vanard, Friedrich, Varian Ilithis, Rock Wraith Abomination, and Corypheus. They may have just thought it was too good a voice to pass up.
For other, more famous actors, it sounded a bit like Max von Sydow to me.
I've been avoiding all spoilers, but I fully expect Corypheus back either as the big bad or as his Dragon, either in this game or the next. The World of Thedas disproportionately emphasizes his role - he's mentioned more often than the Warden and I think more than Hawke. It's like they wanted us to remember him.
(Also, does anyone else think he sounds like a 1980s pop star when abbreviated to "Cory"...? Corypheus already means "conductor" so he's clearly in the music biz.)