So my Amps are set up...subs are booming. As I get ready to buy the next item I have these questions...

1. I see so many opinions on screens. I have no idea really which to go with. I will say this...
The main front screen is going to be used for navigation (GPS) , play lists etc. Not worried about hi quality video play back...just good enough that its clear.
probably a 7, 8 or 9 inch screen.
Are their any that power out like a flip screen you can recommend

2. My MP3 player that I use right now works great. But when I plug it in to charge on the 12v+ plug that turns on with the cars ignition...SOMETIMES I get a buzz. I tried to search the forums. I see different answers. I was going to say its because it shars a common ground but when I hook to the 12v+ that is contantly on it doesn't do it and it is directly below the key'd one