It depends on which WU's you get. I have some systems that are slow AND get bad WU's. Compare that to a fast system getting good WU's and yeah, you could easily remove 4 of your PC's and only lose 30%.
See you got him beat by 4 points. Nice job.
What is going on with these WU's? I keep getting the same 149 pointer (I think) that takes 2 days to finish.