Why throw away emails you've already received, and spent all those processor cycles on? Especially since you've accepted responsibility for them, and SpamAssassin does make mistakes.
Instead use SpamBlocker. First of all you don't waste any machine cycles on the spam at all; you just refuse it before you even read the contents, based on server reputation.
And second, since you refuse to accept the email you've never accepted responsbility for it so it's up to the server trying to send it to you to figure out what to do with it.
And third, when you refuse it you actually send the sending server a message explaining why, so if SpamBlocker has made a mistake, at least the sender knows the mail is being misidentified as spam and can do something about it.
Jeff