I'm sure there are better options for you, but I do happen to own the E17 and MA900 and I'm quite happy with that combo, even if it was my only setup. It was wild to see me unplug the E12 off the E17, since I found the E12 a bit leaner sounding, but faster. I think if neutrality was a target, the MA900 did sound better and sharper/tighter on the E12 and Compass 2. But I found it more enjoyable and musical off the E17, and still very well balanced. I like just having an easy setup of laptop - E17 - MA900, rather than the mess of cables with the laptop - e17 - e12 - MA900
I owned the Magni/Modi, and the Magni was great, but it really did have too much gain for sensitive headphones like the MA900. Schiit should've added a gain switch even if it added to the cost.
I think even off the macbook alone, you'll be happy with the MA900. It sounds great off even a smartphone.