Advice on capable PC for graphic design work

[msgvb]

Hey guys,
one of my friends owns a sign shop and they're looking at upgrading their workstations shortly. they asked my opinion on what might be a good build.

my own graphics experience is limited -- I've run Photoshop and Lightroom on my work PC with the following specs and it works well for the most part:

XP Pro, SP2
Intel D965RY motherboard
Intel Core2 Duo 2.4GHz
4GB RAM (Windows only recognizes 3.25GB)
SATA-II hard drive, 3Gb/sec enabled
nVidia GeForce 7600 video card

I tried out one of the nVidia Quadro cards, the NVS 285 w/128MB memory, but it was actually slower for the 2d stuff than the GeForce card was.
In general though, this build is more responsive than the older P4-3GHz I was running before.

My specific question to you all is with regard to friend's needs, and whether a machine like the one above would work well.
they primarily use Photoshop, Corel Draw, Illustrator -- does anyone know if the Quadro cards work better for vector drawing applications like Corel Draw or Illustrator?

Lastly, would anyone care to share their general experiences and impressions with their current PC hardware builds, what's worked well and what hasn't, or what just wasn't worth the money?

In my own limited experience, I would say that one might get by with a lower end GeForce video card and just 2GB RAM instead of the 4GB, but then again, I'm not sure I've got Photoshop properly tuned to take advantage of the memory. that, or my photo editing needs are simply met with less.