Selecting optimal CPU to couple with a GPU

Dear LAMMPS developers and users

Our research group aim to buy a supermicro having a single motherboard, a GPU (1080 Ti) and two CPUs.

Our simulating system is mainly Lenard-Jones particles whose pair styles have been developed for GPU calculations. However, we know some part of calculations, mostly Kspace, should inevitably be handled by CPU. So, we believe the selection of the best CPU would be the Bottleneck to get the fastest computing system.
Could anybody share ideas on this problem?
A list of available CPUs are as follows:
(1) Intel® Xeon® E5-2687Wv4 (3.0GHz/12-core/30MB/160W)

(2) Intel® Xeon® E5-2667v4 (3.2GHz/8-core/25MB/135W)
(3) Intel® Xeon® E5-2643v4 (3.4GHz/6-core/20MB/135W)

Could anybody say which CPU would provide the fastest calculations in conjunction with GPU?

Many thanks in advance.