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Contemporary Epic (longer books, deeper plots, slower pacing): GRRM And Stephen Erickson. Both are on the gritty side. GRRM is a brilliant writer, maybe a 9 or 10 on the gritty scale. Erickson's more like a seven or eight. Both are good. GRRM favors shorter scenes with a lot of character punch to them. Erickson prefers deeper worldbuilding and more description. GRRM's series is not done, be warned, and it is taking time. Erickson can be more difficult to get into, but is an excellent writer. His series is nearly finished, though be warned that it hops around a lot.
Contemporary Heroic (faster plots, shorter books, fewer characters): Joe Abercombie and Scott Lynch. Both have good, twisted senses of humor. Both are fast reads. Both are Butcher-like (or a little more) in the gritty department. Joe's series is done, Scott's is not. But the Locke Lamora books stand pretty well on their own. (As you like Butcher, I'd guess that you'd like Lynch a lot.)
Now, if you want to try reading widely as you said you might, here are some suggestions: Tigana by Guy Kay. I always suggest this one, as it's my favorite stand alone epic fantasy. If you want to sneak a peek at steampunk, Boneshaker is the book everyone is reading right now. It's quite fun. Zombies and steampunk.
Knights of Dark Renown by David Gemmell is a good stand-alone heroic fantasy novel that shows what gritty heroic was like during the pre-GRRM era. It'll give you some context for Abercrombie and the like. Daniel Abraham's Long Price series (four books, relatively short novels) are a good place to look if you're interested in political-intrigue fantasy with a slight flair of epic.
For literary fantasy, China Mieville would be the first place I'd look, or maybe Gene Wolfe. Finally, if you want to explore historical fantasy, I'd suggest His Majesty's Dragon.
All of these are going to be slightly more toward fantasy in its maturity. If you look at a few and they don't work for you, we can push the other direction toward something more like Eddings or Salvatore.