I would say an amp in car audio is a much larger difference, but probably because the amps built into stock car stereos really, really, really, suck. That said, I could tell a difference between my old receiver's amps and when I hooked an amp up to it. Same difference as a car amp but much more subtle. More dynamic, effortless, tighter bass, and so on. For reference, on a scale from 1 to 10 I would say the difference adding a amp to a car is a 9 and adding an amp to my home receiver was a 4 or 5. Wasn't night and day but definitely enough that I have no plans on ever going back.