It is possible to get 1080p out of a DH2G if its the only interface connected to the graphics card DVI-D port...
(Ive done 3x 1080p outputs using this method: 2x from DH2G and 1x from graphics card direct)
Not tried programming a TH2G in to 'dual head' mode for this resolution... it might work if the matrox software supports it.

3 x 1280x720 is also possible - but you have to use the Matrox tool to program the TH2G as its not a 'default' resolution. - again - connect to DVI-D port.
Depending upon the graphics card and MacPro version - you may be able to run more than one TH2G at 1280x720 (I do with 2008 MP & 8800GT)

see post:
http://chaldee1.gotadsl.co.uk/~richa...ghlight=matrox

Simon