I mentioned in a other post I used the 2637’s for special reasons, I was also aware of the 16core but neither of these is especially popular of common options.There are 4 and 16 core chips in those lines
Intel® Xeon® Processor E5-2623 v4 and Intel® Xeon® Processor E5-2637 v4 are on ARK as 4 core and Intel® Xeon® Processor E5-2683 v4 is a 16 core chip
2640 10-core and 2680 14-core however are very commonly used at least what I see.