Prime lens with 24-70
24-70 is the only lens I have that I use with D600. May be sometime in future, I'll get 70-200 f/4. I want to add a prime to this collection for portrait and general street photography in low light. Everyone recommends 50mm 1.8 but it's little short for portraits and with 24-70, it may never find much usage. The other two lenses I am considering are 85mm 1.8 and 105 2.8 macro.
I'd like to know your recommendations for a prime lens (for portraits) that complements 24-70 nicely. Thanks.