I was pretty much decided on the P8400. But after bigdaddy496s claims of issues, I did some more research. He's not the only one. Additionally, it appears that the P8400 does not support album art the the MP3s are on a USB stick. That is complete crap if it can't display album art when it embedded in the MP3 itself.
Bigdaddy496 suggested the Clarions, but the best non-nav DD unit they have does not support Aux A/V out for a rear screen/sound.
The Kenwood's interface has reports of lagginess. Seen videos of it. At every screen tap, it displays "Please wait" for varying amounts of time.