Jason Stoddard is one of the owners of Schiit and the head designer of their preamps and power amps. Here’s his explanation of the difference between the original Vidar and the Vidar 2. The link is to the specific post on the Head-fi web site; scroll down about 4 posts.
BTW, I have an Aegir and its power is fine with my speakers at my preferred medium volume listening levels (though I do run a subwoofer which takes the bass load off the Aegir.)