no difference between 4k meridian & 400 DVD?

You have hit on the reason that objective testing, particularly double-blind testing, is so unpopular on this and similar sites. Many are threatened by the suggestion that any differences between components/wires are so slight in so many cases that they cannot be reliably confirmed in the face of objective testing.

Those with a financial agenda or fragile ego cringe at this suggestion and will predictably flame away in response. Your ears have enlightened you that in the world of high-end audio, you are best served by your ears and a healthy dose of skepticism.

Let me help you out. Your ears are fooling you . Listen to your 508.24 for a month. Only listen to the 508 .24 and nothing else. After that 1 month is over. Put the 400 DVD back in its place. I promise you will hear the difference. It will be like night and day. I went through this with the 508.24 and the Cal-Cl 20. I thought the ony difference was the bass. Smile i was very wrong. The 508.24 unit is very detail and smooth.

I had the same experience with a Perpetual Technologies P3A with Modwright upgrade and a Marantz CD-63. I couldn't hear a difference. And boy did I want to. But I will blame my hearing before I'd blame the P3A. Too many years of noise. When I was 25 I could hear things that most people could not.

I would agree that you should either use two copies, or two originals to make the comparison. That being said, I have been happily using an RCA DVD player-model 5223 (similar if not very close to the Panasonics in terms of internals) for the past year or so as my CD player. What did I have before? An Arcam Alpha 8SE. I was pretty shocked. The RCA was better stock, and got better still with an aftermarket powercord (Cardas Golden-interestingly being offered up in another thread here on a Musical Fidelity player) and benefited greatly from my line conditioner (Inouye SPLC-one for sale used on Audiogon right now-not mine!). I've also been careful to set it up properly and isolate it (using vibrapods), also tweaked it up a bit by attaching industrial floor tile to any area inside the case that I could fit it to without hampering ventilation or the ability to get it back together-also sandbagged right on top of the transport (exterior or the player). In any event, I think you can get amazing performance (perhaps not SOTA) out of many of these cheap DVD players by paying attention to the above. The cheaper players probably really benefit from filtering or line conditioning as a result of probably pretty weak power supplies in the players. My opinion is that blowing a wad on digital right now is totally crazy, and I don't have the wad anyway. I've listened to some very expensive players and none of them make me want to fork out the money.

Your method has no validity.You did not do a proper comparison.
One more thing Meridians are way way overpriced for what you get.Many units at 50% the cost of meridian are better units.