I think J. Crew is a perfect suggestion for you - I looked at pictures of Katherine Heigl in everyday dress and it's dead on! I also second the advice about mixing high and low pieces - don't be afraid to buy trendier clothes at Zara, etc. In addition to mixing high and low, though, I'd like to suggest that you add some vintage pieces to your wardrobe. Nothing can add dimension to your look like vintage can! I find that the vintage pieces that work best mixed in with a modern wardrobe are outerwear, cashmere, and jewelry.
Have you considered reading a couple of books about style? They can help you develop more fully your own personal style and can offer guidance about core pieces to buy so you can be more thoughtful and critical about your purchases. I recommend Nina Garcia's book The 100 and Parisian Chic by Kiki de Montparnasse (the queen of style a la francaise).
As far as particular brands, in addition to J. Crew and Zara, checkout HELMUT Helmut Lang, T by Alexander Wang, 10 Crosby by Derek Lam (especially for footwear), Loeffler Randall (also footwear), and A.L.C.