Best Practice for RapidMiner workstation

Dears,

I am a mere System Administrator, so I don't know nothing about data mining and stuff.

One of our miners will get a replacement for his workstation next year. And I want to know what would be best for him.

What will increase his performance most?

A) more RAM (currently 16GB, -> up to 64GB is possible)

more Cores (currently 4C8T)

C) more better Cores (currently i7 might be Xeon)

D) more MHz

E) something completely different