looking for a DAC that will add some bottom end

The bass is incredible on the Cullen. Not only is it deep and strong, but it also does exactly what Shazam above says. It articulates the bass, opening it up and resolving all the resonance, the wood sounds of the doublebass or the drums. Not a thud that just dies, but a sound that rings and resonates and sounds like the real thing. It's hard to give this up once you experience it.