I went through a similar dilemma, and ended up ordering a 5900 and having it sent directly to Dan Wright (ModWright) for substantial mods. His webpage lists the mods that he has available. After much discussion with Dan and others who have bought his products, I was convinced to give this route a try. I should get my modded 5900 into my hands in a week or so. I will report back once I have had a chance to break it in and put it through its paces.
The one time I heard a DV-8400, though, it sounded pretty good.
As for Arcam, I totally agree that they are tops in audio quality. As I wanted a "universal" player, though, and I had a credit at J and R (who does not carry Arcam), the Denon 5900 got the nod. I am very pleased with the audio performance of my Arcam FMJ CD23T, though.