tungsten, what you're looking for is what's commonly referred to as a pre-workout, which in
rreality is a stimulant. the good news is they work, the bad news is that comes at a price. one of those costs, as pointed out, can be significant neural fatigue. another is dependency, ie you "need" it to have a good workout. yet another is that the results are temporary. for example, think of people that can't get through their day without a number of cups of coffee; they're relying on the stimulant caffeine to get then through their day.
so should you use them? well that's up to you and what your reasons for training. so while not a steroid, all of these types of products have a similar type of effect in that they allow you to train past the point of which your body is naturally capable. for someone who already takes in a high level of caffeine i would caution against using pre-workouts.