It is a big jump up, and one can easily argue said money is better spent on hardware pieces.

The biggest thing I can see, having thought about it some more, would be if one was insistant
on getting the most 'queue" out of QM and SM doesn't plan to ramp the thing up, then
it might be worth while to be able to do a virtual machine and use it as a second render
queue machine. (since QM won't use more than 1 proc per machine) 

Of course for that kind of money one could buy a cheap pc somewhere too given that you
already have extra licenses....

If you still have your old box...you should certainly think of using that for a QM machine.