ARFCOM deal on the day a week or 2 ago

Picked up a S9 under $250 with the transfer and shipping. Now in have to run some ammo through it to break it in.

Already have a K9 from 1996 when Kahr first came out.

Plus side is the S9 takes the same mags as the K9

Question is what is the difference in the S series.
There isn't much on Kahr website about the S series

Looks like the front sight is staked in, which leads to my next question.

How screw in the a night sight?

Specs say the front sight is plastic and pinned in.
Kahr can install night sights on most of the budget models.