i would like to insert a 2nd gfx card into my computer
and use Xinerama; will SDL be able to open one surface
over both monitors?

Since Xinerama looks like a normal X11 desktop, SDL works normally
when windowed. I think the X vidmode extension doesn’t work quite
right in Xinerama mode, so you may only get one monitor covered then,
but I haven’t tested it myself.

See ya!
-Sam Lantinga, Lead Programmer, Loki Software, Inc.