Marvin invented modern R and B with these two albums. When he went to Barry Gordy with the idea for Let's Get it On, he had originally titled it "Sanctified Pussy." Gordy wasn't wild about the title and told Marvin in no uncertain terms that Motown would not be releasing any records titled "Sanctified Pussy." If you listen to the fade out, Marvin is singing, "I want to get sancitfied." The only remainder of the original lyrics.
I think Tina Turner hit her peak when she left her loser of a husband and went solo. I'm not sure if what she recorded on her own is "Soul" music but it puts anything her and Ike recorded in the shade as far as I'm concerned.
Her stuff with Ike is MUCH better than her 80's hits. In fact, it's not even close.