Rossnz, that's awesome! We have used a FirePro W7100 in a couple machines, and while it ran Resolume really well (7040x2160 - up to around 5 layers 60fps) it started to get buggy with all 4 outputs. (We read the forum, tried 2 active/2 passive adapters, 4 active adapters, etc.) and every time:
-Preview Monitor would go blank (lose fps, test grid)
-Advanced Output features worked (i.e. we could select and move points, mask, transform) but without any active output (i.e. a fully black canvas)
We eventually went back to NVIDIA cards, but I saw some potential in the FirePro's performance. Do you have any settings other than default in your driver for the card?