Few things to keep in mind re: James
For all intents and purposes, he basically *created* funk, which is one of the only times you can pretty much track the origin of a genre to a single person (though I guess Christian Vander creating zeuhl is another example that I mentioned recently). And even for funk, he's not very melodic- he's practically proto hip hop (which is why so many hip hop artists sample his shit), one of the least melodic vocalists ever. So practically all enjoyment of his funk tracks pretty much hinges on your ability to enjoy the groove- not too hard since he had great bands and great grooves but might not be your cuppa tea given your musical preferences.
At any rates, James is required listening for anyone interested in funk but I'd wager that you'll have an easier time getting into folks who were influenced by him (especially since you at least sorta appreciate both Sly Stone and George Clinton).