Dextroamphetamine used to be available as "dexatrim" ...eventually the addictive nature of the substance became readily apparent and over-the-counter amphetamines were no more.. However, let it be known that amphetamines are *extremely* effective for weight loss. Tolerance and moderation are obvious problems, however... but if you ask someone who has been prescribed amphetamines for ADD, most will tell you that they lose weight when they first go on the drugs, and generally have an easier time maintaining it as long as they stay on them.
However.. amphetamines (and all stimulants to a varying degree) are known for their tendency to lead to nutrient depletion with extensive use. If you intend to use them with steroids, which also clearly reprioritize your body's usage of nutrients, I would take extra care to make sure your nutrient levels do not get too low. Between the energy enhancing effects of amphetamines and the strength-enhancing and recovery-time reduction effects of steroids, i could see some problems arising. Also, I don't know a ton about steroids, but i know that they have the tendency to increase growth of the heart muscle.. and amphetamines will increase your heart rate and blood pressure (which may not mix well with the intense bodily stress of bodybuilding)... I'm not an expert, this is just what comes to mind at first.