I changed my AMP from 4308A to 5007. Main reason is "pat pat itching" and want to try the new PIIz format. Surprisingly, it is a real upgrade. 5007 has better surround and more details. It has wonderful bass control, faster speed and more "exciting" than Denon. However, Denon has better user interface and Wifi, that are really useful. Changing the sourround mode of 5007 is crazy stupid.
I think 4810 sure win 4308A. If you plan buy the Denon BD player, sure choose 4810. To me, I use Oppo 83 and they are perfect match. Speaker matching is also very important.