Well let me attempt to answer that Stuart - if your musical taste in soul is broad then you will like the vast majority of records on those labels. I'm probably about 10 away from complete runs on those three and whilst there is some crap, it is most definately in the minority. You can also add in labels like Minit, Loma, Hi, Veep, Revilot, Goldwax, SS7/77, Golden World, koko, Ric Tic, Checker, T/M, Glades / Alston, Westbound (pre 77), Stax and Motown. Not to mention the minor label stuff with fewer releases - but all high calibre - Chi Heat (3), Sonar (3), So Jamm (2 but probably more to be discovered), Roker (5) Soul Clock etc etc....and then we're onto all the other oddball stuff as well.
The point is simple to me - on the major labels I can pull a handful off of the shelf of any of those labels and always find something that catches my ears and mood, be it deep soul, funk, northern, sweet, midtempo, or just a good tune that you cannot pidgeonhole. Some of these will be familiar, others not. As well as playing records that you know and love, to me the quest is always to find something that excites you and that you are either not familiar with, or have forgotten about.
Cheers
Steve