We're the same height though it sounds like we distribute fat differently - i'm a pear and my body loves to pile it on around the hips, bum and thighs! I tend to lose quickly on my upper body (which unfortunately includes my boobs *tear*
I don't do crunches etc at the moment but I have gained definition/tone from holding/tensing the muscles and holding correct posture all day long as well as concentrating on the ab muscles while running and cycling.
I'm down to about 138 pounds and I've begun to actually see the abs outline quite clearly. At 145 pounds my body fat percentage was still too high for any definition. My goal at the moment is about 60kgs or 132 pounds.
I do a lot of cardio though - running 8-10kms most mornings (takes about 40-45mins) and some evenings and a 45-60 minute spin class 3-4 times a week, plus power walking on my lunch breaks, soccer training and games and the odd boxing class.