I would go with a Puerta Cerrada, Aramburu (where the food is excellent and it a memorable "experience"), or Tegui (though I've never been).
I second the PickUpTheFork blog as a virtual BA Food Bible even though some of her "Goods" are "Greats" for me and a few of her "Greats" are "Goods" for me. She's got great photos, entertaining prose, and has eaten around town with the best of them.