I finally found a low-power graphics card with four outputs capable of driving 2560x1440 monitors. And it mostly works, except for one important thing: in Fedora 16 (using the standard Gnome environment), when I enable all four monitors, or three if they are arranged lengthwise, the Xorg X11 server dumps core right away and I end up back at the login screen. This happens when I use the Display applet under System Settings.
I can enable two 2560px-wide monitors side-by-side. I can do four at half-resolution. I can do three vertical (so each is 1440px wide). I can even do 3x 1440px wide plus one 720px wide, I think. But 4x 1440px crashes X right after I click Apply, as does a 2x2 grid of 2560x1440.
This leads me to wonder if there is some sort of limit on the total number of pixels either linearly or in area. It seems like there is, and that the limit might be around 5200px wide or 12Mpx total.
I'm using the free xorg-x11-ati-drv package, and the current stable packages in Fedora 16. The computer has 16 GB of RAM.