Heard the B&W N804d3s ...

I've owned the original iteration of the N804s since I bought them new in '01. After 15 years, I thought perhaps it was time to upgrade to a newer model. So, I auditioned the new N804d3s at a local retailer. They sounded great, and are an improvement over the originals in the areas of bass slam and airiness. However, that step up to my ears is equivalent to about 10-15%. Not sure that that sort of improvement justifies the price ($9K for the d3s vs. $3,500 for the original N804s), although "upgradeitis" tempts me to pull the plug. Is it just me, or does the law of diminishing returns apply in this case? Your thoughts on this or the qualitiative differences between the old and new Nautilus lines would be most appreciated.