Displays (panel)
There are several options for arranging the displays that go behind your panel. If you use external gauges (meaning not undocked panels from inside Flight Simulator) you should go with a network of computers and link them through WideFS from FSUIPC.
If you chose to undock panels from inside FS, you have to attach multiple displays to 1 computer.
You can opt for PCI Video cards
Or you can go for Dual head AGP cards
Which one of these sollutions works best .. I don't know .. if anyone has experience with tests of both solutions, please share here!
Keep in mind that some cards implement hardware acceleration on one screen only.
If you are building a large scale glass cockpit such as a 747 or modern business jet, you might be able to save video cards and space by using the video out of your video card and then splitting the signal into multiple composite lcd displays.