Why $20K? Maybe you will find one for less that you can't beat for that number. Are you trying to impress someone saying you spent $20K on speakers? Maybe you'll find $50K used ones for $20K.
You will most likely be happy with many different models and just find a local dealer who will support you and let you try a few pair in your listening room with your equipment. I would think $20K would necessitate a total look at your system to get the maximum improvement possible.