Dear Paddy
This indeed looks like a potent machine that will be able to handle most Pix4Dmapper prrojects. Of course, this depends on many factors and speed is hard to quantify. Let us point you to this thread, where a similar topic is discussed.
https://community.pix4d.com/t/4384
One thing to keep in mind is to avoid bottlenecks, i.e. having one piece of hardware (RAM, CPU, etc) much slower than the rest: it would slow down the whole process
Best regards