With the standard coding A=1, B=2, ... I=9, J=10, K=20, ..., R=90, S=100, T=200, ..., Z=800, there are only three common surnames that add up to 666 (at least, if anyone can find any others, I would like to know about them).
These are:
Cosgrave, Fox, Waldram.
However, there are many English words which add up to 666, for example Business, Gutenberg, Microprogramming, Newark, Tea-kettle, Three-dimensional, and Tomatoes.
So if a business man from Newark named Fox comes up to you carrying a tea-kettle and a bunch of tomatoes, don't say you weren't warned.
Jonathan Partington, 1988.