A friend had his large Sansui speakers connected to an appropriate size stereo amp using 16 gauge wire. I brought a pair of 12 gauge cables over, and what a difference. The whole system sounded a lot better. Having compatible components (amp cables and speakers) makes a big difference.
In a transistor, a smaller voltage controls a higher voltage. The smaller voltage is the trigger. The transistor makes its output look just like the trigger, only at a higher voltage. When the trigger for one transistor is the output from another transistor, this is called two stages of amplification. A good amp has many stages of amplification, each stage is at a different voltage so the power supply is also more complex and expensive. This allows each transistor to take small power steps, and operate in its most efficient range. The cheap amps have like two stages and a cheap power supply. Its transistors, with a small trigger, control a much higher voltage. This means that the voltage difference between the trigger and the output are much larger. And also, circuit boards and their components come in different grades. Designing circuit boards and systems is an art because some circuits interfere with other circuits, and each circuit needs to be balanced. As you can see, some amps are just designed and built better.
When you turn the sound up to where you can hear it, the differences in amps, cables and speakers start to really show. To those that think there is no difference between amps, this is a drastic over simplification. You pretty well get what you pay for. Good video!!!