Depending on what games you're playing, it's very good to have a dedicated server. Unless of course, somebody just so happens to have a 2-4CPU beast with several gigs of RAM. Not likely, and still not as good as a dedicated box. Something else you'll want will be a good firewalled router. If people need to download updates for the games you want to play, etc, they'll need a protected route to the Internet. The alternative is to download the necessary files yourself and store them on your dedicated server in a SMB, NFS, SFTP or FTP share (depending on your needs/circumstances). Internal security shouldn't be too big of an issue for a LAN so intimate as 10 people, but you might want to seperate your home LAN from your party one anyway. One thing I do when I host LAN parties is ingress filtering at the edge router for SMTP and all well-documented trojans. That way, nobody is spamming on your pipe (getting you black-listed) and you don't have any uninvited guests. But since you're dealing with a relatively small group, you can just handle problems of that nature the physical way, if you catch my drift. ;) You'll also need lots of surge protectors, patch cables, and it wouldn't hurt to have a few extra sets of headphones (somebody always forgets them). Depending on how your house is wired, your room may not have enough amperage to carry 10 PCs. You might need to run some power from another circut in the house also to prevent tripping breakers. And of course, you'll need a place to put all those PCs...
Hope this has been helpful.
-AT