My Ikons feels OK too. I have tested them max 200km only. Last year I had my old Marzocchi AG Strada that was good upgrade in 80's and earlier.
New parts cost some. Good shock important for me if the bike should be used for speeds around 100mph or more. City driving only might allow cheaper stuff. My Ikons look like std CB750 shocks, that's why I bought them. 4-4 will soon be mounted too. The Strada shocks do not look good with 4-4.
I have a repair kit for my old shocks, might be used for a future project.
I have had bad shocks with similar sound, car shocks. I think they had water inside too, frozen winter time.