Which DVDP IS THE BEST SOUND?

Well, first I think you kinda need to quantify what formats you can and can't live without! If you don't need either the SACD or the DVDA, then it makes things simpler. sounds like you're planning on having mostly CD listening though. Anyway, If you absolutely must try to do the "all in one" syatem approach to music/HT system with the DVD player (almost alway's a compromise in ultimate terms), then may I suggest the "beefy" Toshiba 9200 as a transport/DVD spinner, and use the digital out's into some sort of external DAC for improved CD playback! I don't think the DAC's are as good as some of the better externals out there.
Also, depends on what you're hooking all this into! I mean, it's almost a moot point if you don't have a good preamp or speakers to put all this into. And, depending on what you're all hooking it up to, that makes some other considerations worth looking at/discussing.
If you've got some sort of "dirrect" through on your pre/pro, then you might consider the external Dac! (i.e, I see cheep Theta Pro Prime IIa's and MSB Gold link dac's out there cheep for $300 range!!!) These dac's are much much more musical and solid than the Dac's in those DVD players for CD! I know, I've sold these units you're discussing!
Anyway, specify you're rig and budget a bit more. I've seen used Tosh 9200's at around $600 price range! (steal).
Good luck

You cannot go wrong with any of the above players - you need to make a decision on DVD audio or SACD - I have both and prefer the multichannel SACD to DVD audio but they both are good for what they are. On regular CD's the Toshiba may have the edge.

I am not familiar with either the Sony or Panasonic but I do have a Toshiba that is connected to a Theta Casa Nova. I am pleased with the CD sound which is very natural and open. I have not played any DVD Audio but DD or DTS audio is superb. In addition, the DAC in your preamp/receiver will have an influence on the sound.