Since I swapped my Sapphire 5770 for an EVGA gtx 570HD after I tested this earlier today, I thought people might be interested in the Black Death results using the same in game settings (Everything on medium plus shadows, grass, roads, no AA, epi off, ssao off, vsync off) and the new card.
This is with the standard DepthBits =24 StencilBits=8.
Frames 8088, Time (ms) 217650, Min 8, Max 84, Avg 37.161
So my new card has almost doubled the frame rate on these settings.
But then, I put all game settings on Very high, 8xAA, epi off, ssao and Vsync on and got this;
Frames 6366, Time (ms) 216867, Min 9, Max 62, Avg 29.354
Which does me fine for now
I'll try with the 'Bits' altered again and edit this post once done.