There was a 24 output media server on display at PLASA this year (not catalyst) - at about £24K - set up in the same way that Paul was suggesting. - lots of rotated displays producing one large image (up to 4K) - all outputs were DVI (no input however...)

The same result could be achieved with a quantity of Catalysts, TH2G, mix window rotation, offests and a bit of patience!.....
(and at about the same price)

Simon