Just a word of advice, do not rely solely upon a diffuser for your flashed shots. Do learn how to control the flash. A good quality flash will have a lot of user control built into it along with the controls in the camera. experiment with positive and negative EV values while you shoot. Another thing to learn and practice is to use whatever is around you to bounce the flash from. A good example is car shots, typically a car will be parked near another car or a stationary object point your flash in the direction of said object and bounce your flash off of it. You will be amazed the different scenarios where this can come into play if you recognize it and just remember to try it

True to myself you notice I try to show techniques in shooting rather than just becoming hooked on one piece of camera gear. A well rounded, well schooled and well practiced photographer is always going to find a way to get that impossible shot So be sure to practice the techniques available to you