My take is that the difference is so small it's not necessary to upgrade. The only reason to buy the 40.3XD is if you don't already own the 40 series speakers. That said, this hobby does not always bring out the most conservative decision making in many of us. If you have the upgrade bug I will certainly not try to talk you out of it. If you do decide to upgrade I would love to hear your impressions. I personally don't hear much difference.
Happy listening!
Peter
Happy listening!
Peter