It really depends on the level of support you are willing to provide, and the way your network is configured. For instance, at my school, there are 1000+ computers, 1500+ users, 3 level 2 admins, and one level 1 admin. They're job is to manage the Win2k3 servers, the RAID servers, and the OSX servers, plus manage licensing, telephony, internet, network, VPN, WiFi, etc... Granted, they dont really have weekends or breaks, but... It's really more of an art than a science. I would say with that many comps and users, and not knowing anything else about your network, your 3 admins are fine. If you want a halfway, note halfway, decent admin information, you can check out C|Net's TechRepublic: www.techrepublic.com.