If you want to run two SMP clients on your quad .. then yes ..
There are two camps on this issue.
1) PPD Camp - Run two SMP (As long as they meet deadlines) and get more points
2) Work Camp - The Faster the work unit gets done, the better it is for the science.
I know in Windows, we have Affinity changer.
In a GUI Linux, I know you can use taskset.
I am not sure how this is being handled in the Folding CD, but it should work just fine.
I have not seen any body complaining about it, but I don't know for sure.
My two headless Q6^00's run that way. And they get the work done in time. But I have a 3.2Ghz clock on them. I think anything lower than a 2.8Ghz and you will hit some WU's that do not get done in time running 2x clients.