T wave changes in the ECG are non specific and are not equivalent to a major problem if the echocardiography shows a normal heart function.
Stress thallium is a good and reliable physiological test to assess the blood supply during exercise and at rest. A carefully performed stress echo also gives similar information. If the suspicion of blockages in the arteries is high and an intervention like angioplasty or surgery is the likely course of action, angiography is advisable. Coronary angiography again is a simple and reliable test with nearly no morbidity. Multi slice CT, also, is a test to visualise arteries as in angiography with a fair accuracy but does not tell us about the physiology.
Decision for the sequence of tests is best left to your treating doctor.