On the video card, it souds like you want a Matrox G400/450/550. You can get them for $50ish (same price as GF2MX). You most certainly don't want an nVidia card for 2D quality, and Matrox seems like the card for you.
Hardware, I would likely lean towards agreeing with MadRat. I have used VIA KM133, SiS 735, and KT266A on my current rig (also have SiS 630S on my family's Celeron system), and I haven't had any major issues. If anything, nForce/nForce2 would be only better.
And, as someone said, the Athlon XP will spank both the Pentium4 and Celeron in AutoCAD. The Celeron @ 3.0GHz has no chance in AutoCAD 2D against the 1.8A Northwood (which costs $50ish more), And I would add the Athlon XP 1600+, will defeat it as well while costing $35 less than the Celeron 2.0.
I would really encourage you to wait for nForce2 SPP (still get a Matrox G400/450/550, Don't use the int. video, GF4MX is no better than GF2MX in 2D) if you aren't comfortable going with one of the mature KT333 boards.
Just for info, what is your budget per PC??? Jesus is LORD!!!