Other writers of literary fiction. I cannot suggest any specific examples—everyone should go their own way—but I've encountered enough people who think Vonnegut is the end-all/be-all of writing; usually, they haven't read much else.
But I'm a lit snob, so I'm my views are slightly skewed. And Chuck Palahniuk is far too glib and self-satisified for me to stomach; William T. Vollman explores a lot of similar issues, but with a level of humanity that Palahniuk's ultra-hip ironic detachment would never allow.
So hey, you dudes should check out Vollmann. I'll warn you that his prose can be denser than Palahniuk's, but the rewards are plenty. I suggest the aforementioned The Rainbow Stories, as well as The Atlas, as a starting point.
EDIT: Actually, start with The Atlas. It's comprised of numerous essays of varying length (they're all usually short, though). It's a bit more digestible than The Rainbow Stories.