Avoid this attitude. Adcoms see these applicants all the time - high GPA with no enthusiasm for the work. Take the classes that interest you. Don't take upper-level courses you're not qualified for, but don't shy away from challenging subjects you have a passion for. Your elective interests might give adcoms a reason to remember your name when choosing people to interview. Remember, that's what they're looking for - people; not science robots.
In order to succeed you need to dedicate yourself to all of your courses. You can't slip on electives if you want to stay competitive. Whether you can tackle pre-requisites while addressing your interests is an individual decision you have to make, but I was able to explore a number of interests in mathematics and the humanities (including microeconomics) without incident.