Well, since you brought it up, I have the 507s on order. But I have not heard it. The North American dealer has them in stock. So I will should be able to tell you how they sound compared to the 249BE.
As for the 400 Series, HiFi Statement magazine has a very good review of the 407. HiFi+ also has an excellent review of the 407s.
As for the 400 Series, HiFi Statement magazine has a very good review of the 407. HiFi+ also has an excellent review of the 407s.