FWIW, someone in another thread (maybe Q701 or C5/C5D) who was doing some comparisons mentioned he was surprisingly disappointed with the DAC in his Macbook Pro(? don't quote me on the model). So yeah, DAC can definitely make a difference. I'm pretty pleased with my HiFimeDIY Sabre U2, which runs around $56, but I also added the $29 USB Isolator. Another Head-Fier and I tested the Sabre U2 with and without the isolator and decided it was $29 well spent. So, for under $100 you can get that, and the isolator isn't limited to being used with the DAC, of course.
That said, I reckon those recommending the Schiit combo(s) are probably right. I sure love my Lyr