This is a professional workstation for the CG/Video industry. Upgradeability is very important in that field, which is why in fact many switched from Apple to this exact model.
As for power consumption, first, it is built to be used with 2 high-end CPUs, not one. Secondly, in the New Mac Pro, you need external power sources for anything that is not included anymore (which is a lot).
It saddens me to see that Apple is not in the Pro/upgradeability market anymore.