I feel as if that card would be hard to replace by the looks of it. Have you opened the case yet to see if the card is removable?
It's upgradable, for sure. Here's the link to the PC at Tom's:http://www.tomshardware.com/news/Dell-Alienware-Mini-ITX-PC-Gaming-X51,14511.html
The power supply is limiting. I could buy an upgraded 330 watt PS for about 100.00, but I wasn't sure if I needed it. Sounds like I might if I want to keep this monitor.