Well you could probably build a couple systems for $2K.
Athlon XP 1.73Ghz
Chaintech Nforce2 IGP motherboard
512MB PC2700 DDR Ram
Western Digital 120GB 7200RPM 2MB cache hard drive
Keyboard/Mouse(logitech opticals are cheap & very nice)
The motherboard includes pretty darn good audio/video/lan for it all being integrated on the motherboard. Nforce chipset is designed by nVidia and supports dual-channel ddr memory = big performance boost. Also the onboard video is decent enough to play many recent games on, it's equal to about a Geforce4 MX(which is around Geforce2 GTS) speeds. If you feel the need to upgrade you can since they leave the AGP slot in. The sound is said to be quite nice and rivals add-in solutions(creative, turtle beach).
If you need Premiere, you should buy it in a DV200 bundle. That will run you about $250 per DV200. DV200 is a DV capture card as well. Premiere is normally about $550.
There is also the option of not getting any CDRWs for any of those comptuers and just investing your money into a single DVD-RW drive. Which could backup your projects and allow you to master DVDs.
I would forget about having a "3x200GB(600GB) server". Unless you already have it. Maybe it would be useful for storing backups. What with each computer having 120GB of space, I don't think you'll need the server. Also even over a 100mbps network, it's still no where near as fast as having it local.
If you just need one computer than I would go all out and get a GB of DDR, dual Athlon MPs(XPs can be used put aren't garunteed) & a SCSI setup. Oh and a Radeon 9800 Pro.
I think the system I listed above will give you the best bang for your buck. You can use one of them as a server if you want. Get three then max out the disks on one of them.