In their book, Elmendorf, Kriz, May and Mandell describe a useful category of spectra, called S-modules, where S is the sphere spectrum. Ring objects in this category can be identified with spectra with an action of an $A_\infty$-operad (if I understand correctly) and commutative rings can be identified with spectra with an action of the $E_\infty$-operad. Has anyone written about $E_n$-rings in this category? In particular, are there nice model category structures on categories of $A$-modules and $A$-algebras if $A$ is only an $E_n$-algebra? Can this perhaps be shown by somehow trapping this model structure between the nice model category structures on commutative rings and associative rings?