Typical aero levers will give you about 10 percent more braking force (at the cost of 10 percent farther travel) than non-aero levers.

You can improve almost any set of brakes with new cable housings and KoolStop pads. The rear (Weinmann 999 centerpull) brake on my Peugeot had become almost worthless before I replaced the cable housing, which made a HUGE difference. (I hadn't really noticed for awhile, because I normally use just the front brake, unless checking speed on a long descent or trying to avoid a disastrous front wheel skid on wet pavement.)