+1....sell the 150-500 mm and buy either the 70-300L, or the 100-400L if you choose focal length over aperture. But, as you stated you want aperture over focal length, some have used the 70-200 f/2.8 IS II with a 2x TC to get to 400 mm. From what I have read and seen posted here, that can produce very good results at 400 mm, but not as good as a lens that gets you there without the TC.

Of course, I can see filling your void with the 85 f/1.8 as well. It is very well regarded and near the top of my wish list.