Copy from an other 3d:
i did it on my poweredge 1900 (2007-2008), i get it for free like yours, mine's got 3 pci express x4 (x8 shaped) and a pcie x8:
-i bought a 5€ ati radeon hd 3470 ddr2 512mb (most of radeon hd 3xxx 4xxx 5xxx are supported)
-i cutted it to fit on a x8 pci express slot, the bios recognize it
-i put that on the pci slot 1
-i put a gainward geforce gt730 2gb ddr3 on the x8 slot (this graphic card is native x8 available..60€ more or less..not recognized from bios)
important: With the radeon plugged i am able to run windows, nope with only the geforce, because the bios can't recognize it and it gives just a blank screen.
-in win (using the radeon video output) i installed the geforce drivers, win recognize the second card installed... reboot
now you got two cards installed... well, how to make work the best one?
win recognize the second graphic card's output as a second monitor, simply assign the better gpu output as primary display and de-activate the other one (in control panel, etc...).
now you got a fully working ddr3 2gb graphic card on an old dell poweredge... i'm able to run starcraft 2 hots with mid-high settings!
remember that the cheap'n'unuseful radeon MUST be plugged in to let win started, because if the bios doesn't find a supported pcie gpu, it gives blank screen next of the boot.
my rig is fully working, but during the bios boot i'm not able to see nothing from the display, because the bios uses the radeon output (unplugged), when win loads the geforce starts working. i don't even need a sound card, the hdmi does it!
Davide