Thanks All for the replies; much appreciated!
All things considered, I'd prefer a solution which can survive an upgrade or two, so I'm leaning towards Win7/64 with an external controller if possible. Win7/32 wouldn't be awful, as I can always reformat and reinstall when the time comes, but I'd still want to use an external controller to consolidate the startup pain.
As far as XP goes, my firewall is fine but end users are end users, so I'd really have to lock it down to avoid the malware they might ask for when nobody's looking. I want connectivity for program and OS updates, remote monitoring and admin. Isolating/locking down XP would also be pretty expensive for my client as they're paying me by the hour, so I'd need a pretty compelling reason to go that route.
Wes, I'm a big fan of the HP Z-series workstations and also more interested in time lost than money spent. I've got a few i-7's out there with 8GB RAM performing beautifully. I haven't had the need to add a discrete GPU to these PCs; can you recommend one, or should I wait and see how the integrated graphics hold up? The end products will be home décor accents (nic nacs. office desk stuff, coasters, etc) so no need for extreme tolerances; I'm sure AutoCAD would be huge overkill for their purposes if that helps.
I've also been impressed with HP's IPS monitors; would 1920x1080 be sufficient for creating these types of products?
Thanks again for all you help!
Bruce