Just one note about Peerguardian. They add ip's to their blacklist but do not go back & double-check them any time afterward. Thus, they do in fact block some good ip addresses. Many people including spammers use dynamic ip addresses which change after a few days or weeks.

Second thing of note is on some people's systems, PG may use up a lot or system rescources. However, it will definitely block out a lot of bad ip addresses.