I apologize for bumping this old topic, but I have done quite a bit of research on this, so I want to share my experience.
I had recently brought all the potential candidates, unfortunately, the ailing CD3400 turns out to be the best sounding, followed by the Panasonic (couple different models have same innards, my sample was 870 - splash proof version of 570).The hypes from Head-fi prompted the inclusion of DT25. I won it on Ebay https://wheelstips.com/best-car-dvd-player and the seller graciously took it back, a lost of $10 shipping. The Sony skips at the slightest move, and the high frequency is rough, very antiquated brick-wall filter. One thing that I haven't tried: those portable DVD player may have better sound than CD player if used on CD only. Try the Panasonic/Sony/Pioneer without the screen. I was shocked how good a Pioneer $199 DVD player the 525 compared to my Philips SACD-1000.
Especially for those who still stumble upon this post in order to find information. Since I see the author for 4 years already most likely to buy a player=)
Consider the options among SONY and Sylvania. I think these two firms are the most competitive now. For example, I'll take 2 models.
Sony BDP SX910
In general, the DVD is very good, the display is much better compared to other brands, it reads well with USB, I tried the maximum of 16 GB, the headrest is super-mounted, I did not see any DVD in the set, the battery actually holds 5 hours, from minuses very noisy drive with a disc.
A great model. The picture and sound quality are excellent. With USB it reads everything. Two headphone outputs, which is very convenient, for example, in an airplane. The battery is generally higher than any praise - during the 7-hour flight almost continuously watching the movie) Plastic fastening in the car - also a plus.
if you want to see more information about these and other models, go better to this top 5 portable player and decide for yourself.
Thank u for attention!