There is good synergy with the two. Khan has an incredible amount of chill which so far seems to meld well with Stark Black. However keep in mind I’m only on ST1. By ST4 I’ll know much better if this is a good long term pairing.
Also, although I’m productive it’s not on the level of an Emperor/Stark Black. It’s not good or bad just different.
One of the things I really enjoy about Khan/Stark Black is I think about lifestyle a lot more. I sat down recently and made a life list which has been helpful with overall decision making. Also as a thought experiment, when making decisions I think about how I’ll feel in a day, week, year and beyond. Which has reduced the amount of will power and motivation I needed in the past.