My experience has been it's a bit of both. With the rig in my signature I was getting 30-40 at a busy airfield(the slowest point for me), much smoother than 1.2, but some noticeable stutter when panning around. Settings mostly high but with lens and dof off and aa low. I have now upgraded to a 6600k and 16gb ram and no matter what I do (except dof) I can't get it to dip below 60fps (vsync locked) and it is smoother than any flight simulator I have ever played (and I have been playing for over 20 years). It was working great with the old rig and I didn't really need to upgrade, but I am glad I did, because of the smooth feeling of no fps changes. The other thing to think about is your brain gets used to what you have and smooths over many of the problems.. So if you have the money go for a big rig, but it's not essential and with 1.5 even old CPUs are getting great results.