Software available to check digital audio 'quality'?

[cgregory4]

My new system is operating with HP ultrabook >> Berkeley Apha USB >> dacMini >> Bryston integrated.

 

My question: I will be shopping to upgrade my dac. The Alpha USB has multiple output options, so I can use most any dac. Is there a specific input spec that lends itself to using available digital software which would evaluate the quality of the digital signal to the dac? A sort of digital equivalent to the analog 'THD', displaying and comparing various digital signal 'qualities'?