Gabor,
The missing part was that the kernel option (or parameter)
pci=nommconf
needed to be added. (Maybe this is not needed in 2.6.16 anymore (but
it probably is)...)
Then it showed up in lspci.
And XF86Config-4 can handle it nicely.
I even found a web page where a guy describes how to run 3+ monitors
all in one desktop (xinerama? no X screens) AND all OpenGL accelerated !!
He said something about NvAgp vs apgart - and some other tricks...
(Maybe this is nvidia specific - but mixing nvidia and ati should also
work)