Shock Absorbers (KYB, OEM, Bildstein, etc) best bang for buck ?

BMW Inc looked at the undercarriage of my 2000 528i (185,000 miles) and nothing is at wear or worry ... it is holding the wheel alignment of 5000 miles ago .. just the shock absorbers are getting weaker but are
not leaking any.
The car science I know about the nitrogen gas system is about 20 years old, and I don't need to toy the car up with fancy suspensions that are very pricy at todays market.
I have done KYB before, a real good shock that takes a few hundred miles to soften and click in way back in the day. There are newer off market manfactures that have better car science going on with them for the money.
Soooooo .. is it better for mechanicals and money to get BMW replacement parts (these have done rather nicely) at the BMW store and have the pros fit them in.
At the same time I am going to have them swap out any torn rubber boots, clean out the wheel grime, respin them with weights on the inside on the rims, and get the same air valve stems put on each wheel since they are going to have to bust the tires anyway.
This makes necessary an alignment as well to finish it properly and put it on the road.
Oh ... the Power Steering Master Unit and hoses were replaced a bit ago (as it was leaking) .. however the other end of the power steeting where the rack and slave unit is ... so far .. is doing well and not a worry.
In for a penny, in for a pound.
Replace this power steering slave unit in the steering gear any way ???
Thanks for your sight and insight.

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