In short, it's not all about the gear.
The better your room or better put the bettering of your room the better your system will sound.
Over the years the best sounding systems (not necessarily expensive ones) have always been in great rooms. Beyond a point the gear doesn't matter so much as the environment it's in and how it's set up. For 15-20K you can get it done but please consider thinking of your room (and power in it) as a big part of your system.
The better your room or better put the bettering of your room the better your system will sound.
Over the years the best sounding systems (not necessarily expensive ones) have always been in great rooms. Beyond a point the gear doesn't matter so much as the environment it's in and how it's set up. For 15-20K you can get it done but please consider thinking of your room (and power in it) as a big part of your system.