Bilsteins are high gas monotubes. Expect a rougher ride, especially with the PSS9 stiffer springs. Handling will be a lot better.
We have Bilstein B8s in the 993 and are a lot happier with them. But the 993 OE shock supplier for the US market is
MONROE.
...and they were definitely used up after 98k miles and a LOT of track days.
My two cents are that you'll probably be best off leaving it alone until you feel like you want to do something.