seems to be best in groups, problem is the impact on a network. Truth is some av companies will "out scoop" the others on some viruses, and other times there defs. will be the last to get updated. AV is a crapshoot, Symantec seems to have the best reputation, (or at least the biggest market share) but Trend Micro, Sophos, etc. seem to hold their own. Overall I would recommend two virus scanners (from two different companies) for mail servers and one for the enterprise as a whole. As long as you have it constantly looking for updates thats all you can really do.
(this is not a commercial and I do not get compensated) you can't get much better than a barracuda spam filter. I was skeptical at first (and loathed the commercials they play incessantly) but the truth is, it works.
It allows you as the admin. to set rules and tweak existing heuristics, which stop the spam, before it enters your network. A common issue with spam filtering is false positives and the loss of critical good email. This is not an issue with barracuda though, since it sends an email daily to each user letting them know what was blocked. If there is a good message trapped by the filter, the user simply needs to click whitelist, and the email is delivered.
I love getting my hands dirty and making things work without a fancy gui, but spam is not my passion, and if I can stop spam from becoming someone's full time job (monitoring and retrieving messages) then I couldn't be any happier.
I'm sure someone can recommend a good hands on course (believe sourcefire has courses throughout the country) that will give you the knowledge you need to understand how IDS works, or in the very least give you enough information to get you through an interview. Hope this helps. Good luck!