i'm just going to have to disagree with the multiple assessments that such a rig is overkill for photos. once you've worked with a library of over 12000 RAW photos (about half being 8MP and the other half being 16MP) with a workflow consisting of aperture, photoshop, imageready and illustrator on a daily basis (usually in that order), then we can talk. don't get the false notion that photo work isn't resource intensive - OC runs on a powermac much like mine and a 15" powerbook, and the last time i checked, he did primarily photo work.
but keep in mind, this system isn't necessarily dedicated to any one media (photo, film, etc.) - i use it for everything. clothing design (try working with 300dpi 20inx28in vector artwork on a G4, see how long it takes you), photo, video, graphic design, print design, web design, as well as plain old poking around the intarweb and school work. at some point, though, in order to do professional work, you need professional equipment. i originally ran on a G4 mac mini and a G4 powerbook. awesome machines, and it made for a great compact setup, but after about a year as more work and projects began piling on, i desperately needed to upgrade - when it takes 15 minutes to transform a path in illustrator, things need to change.
i keep a lot of programs open at once because i literally might need them at the drop of a hat and i don't want to wait for them to load - the 25MB of idle memory that illustrator takes up is preferable to the amount of time it would take to load from a dead stop.
as this is ns, i know most of you kids won't bother to read this.