What I had in mind: JBL LSR305 speakers. Regularly available for $260/pr. Sometimes a bit less. Driven by an Emotiva XDA-1 DAC. I see the XDA isn't available now. It was good, both because it sounded surprisingly nice while having balanced outputs. Connection to the JBLs which are active speakers was easy. I suppose I was cheating a bit as you still need a source, but the XDA had USB and your usual other inputs. A phone, tablet or computer could be used and nearly everyone already has one of those. Currently there are other USB capable DACs available to keep the price to $500 though I haven't heard them. Emotiva makes a Big Ego for $219 which is 32/384 capable with multiple filter options. No hands on experience, but I am guessing it would do the job nicely.
So for $5-600 you have plenty of options to net audiophile sound quality normal people aren't accustomed to hearing. Improvements from there on up get expensive for increasingly small differences. I haven't heard them, but Emotiva makes a nice speaker getting good reports from lots of people for $299/pr also active no amp needed. Measurements in the Stereopile review certainly look rather nice for so little money. ELAC speakers are available in that price also getting excellent reports. So the bottom end of what is quite good in the modern world is not that expensive. Adding a decent subwoofer to these kinds of speakers moves them further up the ladder of sound quality.