Having worked with workstations and desktops - they're pretty much the same as far as interfaces go. You can load a regular graphics with the right interface into a workstation.
The differences are workstation cards may be better at some workloads (which doesn't matter in your case) but there's little stopping you from tossing a spare quadro or fire into a gaming PC or a gaming card into a workstation.
That said, workstations can be a little unusual - I'd check to see if there's a GPU power connector available (you can convert these from a spare molex, or presumably sata power supply), and your PSU may not be compatible with a standard ATX, especially if you're running dual processors.
At the 80 dollar price range, eh, you shouldn't be running into too much trouble with any common PCIe GPU