N250GT,N260GT,N275GT,N285GT,N295GT - all these new cards are better than 9800GTX. Most of these cards have pre-overclocked editions as well from various manufacturers making them even faster than the default Nividia guidelines.

http://www.tomshardware.com/charts/gaming-graphics-cards-charts-2009-high-quality/3DMark06-v1.1.0-3DMark-Score,1340.html

Found this "fix" reading wikipedia. Open the command line editor (must start the save with your Xbox360 controller disconnectored) and type in tcl. This will enable noclip and allow you to simply walk through the door. Type in tcl again to disable noclip. I managed to complete this DLC without any further use of this command.

same problem - supposed to be a hologram here