I don't think the whole hi-rez, digital link, bass management is going to get sorted out for another year or so. I'm sick of waiting. There are only a couple firewire equipped players and nothing to plug them into but $4k HT receivers. No thanks.
For under $150 it's hard to beat the 563A. Just make sure you get one with the latest firmware update to avoid problems playing back recently released DVD-As. It sounds O.K. out of the box but really has potential with some modifications. I've put about $200 worth of transformers, caps and hexfreds into mine and it's now singing quite nicely. Certainly sounds better than any of the other digital sources I've had in my system over the past five years (DV45-A, SCD-C555ES, MSB Link DAC, all unmodified).
The only thing that bugs me about it is that many of the playback options (repeat, stereo/m-ch switch, etc) are buried in a gui menu requiring a monitor. But this is probably an issue with most if not all multi-format players.