Hi,
X-Plane 8 runs very well on my same spec iMac. I use it with a MS Sidewinder Force Feedback joystick with no problems at all..
I also run MS Flight Sim 2004 via bootcamp at nearly max graphics settings and it looks and flies very well using the same joystick.
FS X is also loaded but I am not overly happy with the frame rate when using the Level D 767 addon.. It is very taxing on the graphics system and is just good enough to run at fairly moderate settings..
MS Combat Flight Sim's all work well via bootcamp..
Hope this helps..
Cheers,
Nelson..