[GoldenGuy66]

How would this combo sound okay without the DAC?
 
Would It sound BETTER than what I have so far ? (HD 558 directly plugged into macbook pro, I think this sounds pretty good to me already 

)

 

[PurpleAngel]

  How would this combo sound okay without the DAC?
Would It sound BETTER than what I have so far ? (HD 558 directly plugged into macbook pro, I think this sounds pretty good to me already 

)

 
Usually Apple products seem to come with better built in audio, then a PC.
Would an external DAC offer better audio quality then whatever DAC is built into the Mac, chances are yes.
But an external DAC is optional, so you can skip getting an external DAC, for now.