The Denon will have far superior room correction (Audyssey MultEQ XT32) VS. Sony's DCAC calibration which will have a big impact in the sound of your system. The Denon has pre-outs so you can add an external amplifier down the line for more power.
I'm also sure the Denon will get closer to the acutal rated power specs - a quick look at the back of both receivers reveals a power draw of 675 watts on the X4000 and just 240 watts on the Sony.
There's a ton of information on the new Denons in the official thrrad here. Take a look for a complete rundown. IMO they are not directly comparable. If you're looking at Sony you should be looking at an ES series AVR to compare.
ht Panasonic 60" ZT60, Monitor Audio: Silver RX6, RX Centre, RX1; Martinlogan Dynamo 700, Marantz SR5006, PS3, Oppo BDP-103D, Panamax M-5100PM
2ch Sony 32" W650A, Sonus faber Toy Monitor, REL T3, Marantz PM8004, Sony BDP-S1000ES, JVC T-X3 tuner, Apple TV, Peachtree Audio DAC•iT, Panamax MR4300
pc Monitor Audio Radius 90HD, Audioengine D1, FiiO A1
+ Sony 65" XBRX850B, Sony BDP-S5100