having 3D acceleration should slightly improve the render times as they definitely won't get worse
Well, if you have GUI running, then you might see few (low) percent decrease in rendering times, as it might waste some CPU time drawing the GUI (which could be used rendering).
But it's been long time since I did some benchmarks, but isn't it possible to run blender from command line without a gui, and tell it to render specific (given from command line) scene?
That way it won't use gfx card at all, so you can see if you can get few percent faster renders :lol:
Doing:
blender -b scene.blend -f 1Will render the specified frame (1) of the given scene to /tmp/0001.png
With
-t you can specify amount of threads (how many cores will be used)