Just wanted to second a few suggestions that were already made. I think Untangle would work well for that environment, (although the AD integration is a billable feature which you may already have noticed). Couple that with OpenDNS like YeOldeStoneCat mentioned...
If you're interested in certifications, check out this site...
http://www.techexams.net/
They have some decent free study materials, book recommendations, as well as active forums dedicated to each cert.
A good Linux distribution to start with is Ubuntu.
If your games don't have a Linux client, then you'll likely be playing them using WINE. You can check your games compatibility here with Linux/WINE here:
http://appdb.winehq.org/
Go into Control Panel -> Network and Sharing Center.
Check the settings for:
- File Sharing
- Public Folder Sharing
- Password Protected Sharing
You should be able to clear it up there.
Do you have a pool of public IP addresses available?
Assign each of those domain addresses a different IP, then just alias the multiple IP's on the router, with each being forwarded to a different internal server.
So DNS-wise for the public IP's you have...
1.2.3.4 = mail.company.com...
I know this has been posted before, but it bears repeating...
http://www.pcworld.com/businesscenter/article/146256/vistas_despised_uac_nails_rootkits_tests_find.html
The quotes of interest:
The emphasis on the 'none..' part is mine, as warning to those who think they're 100% secure...
Newegg has the same card for $162 ($167 with shipping) but also a $20 mail-in rebate. :)
http://www.newegg.com/Product/Product.asp?Item=N82E16814150106
Here's an article from 2003 dispelling "wireless security"
http://www.oreillynet.com/pub/a/wireless/excerpt/wirlsshacks_chap1/
Note that there are some people in the response area that dispute the speed of the hacks, but they have been proven wrong over time. There are even better software...