I have the 4400 and I feel it's decent for the price. Nowadays, alot of people think that denon and marantz share the same circuitry with minor tweaks but different faceplates. I am not sure if it's true or not but the marantz seems to command a premium for similar spec models.
I think the 4400 is a good model and I am happy with the purchase, especially for the 800 or whatever they are going for nowadays. My setup is similar to yours and it replaced a older, higher end onkyo due to the need for 4k support. I feel the build quality and sound are better, not drastically so, but noticable enough, especially when effort is put into the calibration.
If I were to do it again, I would demo it against a Yamaha, whose last year upper models can be had for similar sale pricing to the denons and seem to be receiving excellent reviews. I did not do this, but often wish I did.
Good luck. Obviously ask yourself what features you really need and if at all possible try them before you buy.