Even if you can work this out, you may not get the results you want.
Dunno about gamecube, but SOME Xbox games support a high resolution of 720 lines of resolution on a hd tv... your cinema display is gonna smoke that.
Console games take full advantage of the lack of resolution available on TVs. TVs have a certain amount of anti aliasing due to lack of picture quality. Keep in mind that modern consoles can crank polygons, but they're doing it at a lower resolution... which translates to faster game play.
Having a killer monitor displaying console games is just going to show the relative lack of graphical quality inherent in console gaming.
Not to knock consoles. I play games on consoles, and do computer oriented stuff on my Macs. each has its strengths.