I doubt the stabilaizer has anything to do with your knock. Someone who is familiar with lowering their car may be able to help you here. One of the reasons I am hesitant to lower mine. I know Andrew had Eibachs on his when he had it, you might want to PM him and see if he can enlighten you.
The steering damper is very easy to replace. With the money I save on oil changes I'll probably do mine every spring when I'm under the car doing the oil change, its very easy and it does make a difference.
Pat