Multiple outputs like the 'Picturall Octo' is possible from catalyst - to a limited extent - BUT only by using mix windows and a screen controller such as:
http://www.iiview.com/index.php/prod...all-controller
or multiple Matrox TH2G
(see thread http://chaldee1.gotadsl.co.uk/~richa...ead.php?t=1698)
SO currently with Catalyst answer to multiple graphics cards is is no.
The 'Picturall Octo' server is an interesting system - it has an excellent output 'mapping'. It has custom MPEG 'type' enoding to achieve 4K resolutions. Its based on a linux system (although not mac). They claim 8 layers of 1920x1080 MPEG2 off a standard SATA drive and the outputs do appear to be in sync.
Do contact me if you require further info...
Simon