Just to toss an alternative opinion out there, here's one from 2004:

http://www.peachparts.com/shopforum/vintage-mercedes/108550-w115-front-shocks-bilstein-kyb-sachs.html

Lots of opinions out there, and not everyone agrees. I'd rank KYB Gas Adjust shocks with Bilstein HD in terms of firmness, FWIW. Bilstein Comforts and Sachs/Boge are softer. I've used KYBs on a couple of cars. The ride isn't unpleasant at all, IMO. My experience is that Sachs and Bilstein comforts aren't as durable as heavy-duty shocks.

An old friend told me he put Monroe shocks on his W111 and W108, and I never heard him say they didn't live up to his expectations.