It had that much hardware in 2008 and only $580? Or are all of those after market upgrades? I prefer to build my own Windows PC too. I built one recently but had to put in an old GPU while I wait for AMD or NVIDIA cards to be available, if they ever will.
I added the RAM, SSD and PCIe card as those are all modern components. USB 3.0 wasn't around back then. The system has a listed max of 24 GB of RAM because 8 GB DDR3 didn't exist back then, at least not at the retail level. SSDs were pretty uncommon back then asa well. The thing is that all of the components, years down the road, are really cheap now.
I thought that it was a fantastic deal back in 2008 - it originally had a Hard Disk Drive and 9 GB of RAM (triple-channel memory). They were sold more as server desktops than consumer desktops. I wouldn't touch the newer XPS desktops - I don't like the new hinge design as it could be a long-term reliability problem and everything is too compact so maybe thermal issues.