JGrabowMST has made a few good points regarding using the Asus Z9PA-D8 vs. Asus Sabertooth and the fact that you can put 2x Intel Xeon E5-2620 into a Asus Z9PA-DA vs. only 1 Intel i7-4930K in the Asus Sabertooth MB.
Of course if I went with the Asus Z9PA-DA, I'd start out with 1 Xeon E5-2620 and then bump up to another later (if needed) but that fact that one can do this makes the Asus Z9PA-DA very attractive!
Thoughts?