A 78-year-old man reports exertional chest pain, dizziness and two recent episodes of syncope while walking up a hill. Examination reveals a slow-rising carotid pulse and a harsh ejection systolic murmur loudest at the right upper sternal border radiating to the carotids. Echocardiography shows severe calcific aortic stenosis with a valve area of 0.6 cm² and reduced exercise capacity. What is the most appropriate management?