https://www.pugetsystems.com/labs/articles/Adobe-Photoshop-CC-Multi-Core-Performance-625/ I see that Photoshop require higher frequency instead of multi cores unless I use Premier Pro. I guess I should get X5677.
Yes, but this test shows that exporting in Lightroom really benefits from as many cores as you can throw at it, and you mentioned exporting in LR as something important:
https://www.pugetsystems.com/labs/articles/Adobe-Lightroom-CC-6-Multi-Core-Performance-649/
So you want both high frequency and as many cores as you can get.