Z820 Cpu/ RAM spec

Hi all,
We work in a corporate environment and IT have a lease deal with HP, so we can get a Z820 to upgrade our ageing current PC.

They can ship with different CPUs… which CPU do people think is the best suited one for Nuendo on the Z820?

Beacuse it is corporate accounting money, I am not too concerned with price.

Sorry, I am not a CPU guy, I just need guidance.