If you are looking to fight spam coming through your emails system, I recommend Barracuda Networks.  We have been using the Barracuda 600 for about a year and recently went with a Barracuda 400 for some additional domains.  Both of these units have worked well for us and we have been happy with their performance.  The Barracuda 600 has been out performing our previous set up which was a farm of Spamassassin servers.  Go with Barracuda, they are a little pricy, but you get what you pay for.