Given what I said in your post on coolant, when it comes to mechanical parts aftermarket is not always as good as OEM, and thats all car makers, not just Volvo. I've put aftermarket master cylinders and alternators in Fords and GM's and had to try two or three before getting one that worked. However, I haven't really had to do much stuff to the suspension on my Volvo, so I can't really say. I just did the struts and shocks, including all the mounts. Struts and shocks were Sachs (OEM for Volvo) but the mounts were whatever aftermarket brand that FCP Groton sells. So far no problems. I also did a front wheel bearing/hub last year, that was some German aftermarket brand that my Volvo indie buddy got for me, so far no problems there either.

I would talk to a Volvo specialist and see what they say. Some will only use Volvo brand, others may have some knowledge of which aftermarket suppliers are good and which to stay away from.