Here are a number of posts that ought to help point you in the right direction - some are a bit dated but mostly still accurate.
My favorite place up that way is Timo right in Sunny Isles - Mediterranean bent, menu changes pretty regularly, classy but comfortable, great wine list.
A couple newer places I haven't tried yet and may not be mentioned in those threads - Il Mulino (in the Aqualina, Sunny Isles) and Michael Mina's Bourbon Steak (Turnberry Aventura).
re: Food on the brain
First, I would not say that South Beach is the dining mecca of South Florida. Some of the best restaurants in town these days are in less established areas.
Having said that, Timo is one of my favorites in any part of South Florida, and just happens to be in Sunny Isles, and I've heard very good things about Bourbon Steak though I can't vouch for it personally.