Currently, I'm using dspam linked with amavisd-new. All emails get processed by amavisd-new, but it passes them to dspam. I have a nice history of logging, where I can mark emails as spam or retrain if they are incorrectly identified, but I've not got anything appearing in the quarantine.
Amavisd-new is doing the quarantining, and storing them in a directory, which means I'd have to manually check there to get it back again.
If you're using dspam, how did you get it to quarantine? I'd be interested to know