its getting to be a balancing act. Cubase does scale well (when all is right)
ideally you would want a single 6 core High GHz processor. easiest advice I can give without confusing the point.
the 4930K is presently the best overall for power and cost.
the 4930K overclocked is near impossible to beat without getting into 10-12 core single processor. and even then its dollar foolish