A small heads up, setting irradiance caching to 0 will reduce quality of ambient occlusion - at least according to the manual, which is occasionally wrong.  As far as I remember when fooling around with it that seemed to be true though.  Also I've found that enabling AO for an IBL light produces pretty "dirty-looking" shading, although maybe there is a combination of settings that works well that I didn't find; I think it's a lot cleaner to put AO on the material where you want the shading to occur.

I have also found that sometimes Smooth Polygons will cause very incorrect AO shading to be applied on some models, so for those models I turn it off (DAZ cyclorama comes to mind).

My Freebies