Top end GPU is not realy needed, except by a very few!!!!
Extreme end GPU's are not needed by the great majority of Architecture and Engineering firms. The majority of the CAD staff are not "power users" so the majority of work can be done with a very good gaming card.
Out of a 100 seat firm it is probable that only 10 full workstations would be needed.
Don't let those workstation salesman sell you goods you do not really need.