> But I cannot notice a major difference between the $100 system, and say a $100k system (or whatever audiophiles spend).
You definitely will, but at lot of it will come from the fact that the latter system will be set up well in an isolated room with proper speaker placement, while the former will be some speakers thrown in a living wherever they fit.
Sensitive speakers are the huge difference, because they will give you more detail at normal listening amplifications. A good pair of speakers and 25-50W of amplification power is more than enough for most domestic scenarios, and even then you'll be using it with volume in half. The difference are the speakers - and sensitive speakers are expensive compared to a "$100 system"
You definitely will, but at lot of it will come from the fact that the latter system will be set up well in an isolated room with proper speaker placement, while the former will be some speakers thrown in a living wherever they fit.