I wouldn't worry about breaking the cheaper components. The more expensive components are not necessarily stronger, but they are lighter and smoother. Your weight also doesn't matter with components either. The shifter just moves the cable that moves the derailer that moves the chain. None of them carry any of your weight. The cranks just transfer your leg power to the chain. The only exception that I can think of would be the brakes. The brakes have to be strong enough to stop the more kinetic energy you have.
If you can afford the higher level components, things will be smoother which usually turns into more enjoyable which turns into more time on the bike.