Is it possible? Both in and working. If it is possible how would I do it. I got one deck in my cupholder slot and was planning to get an in dash player for the top.

 

why would you want to have two??

 

Actually it was quite common practice back in the "golden era" of car stereo when CD players just appeared on the market. Can it be done...sure. Would most sane people do
it probably not.

I "assume" you want to have a video display in the upper with the radio below.
There are a few ways of going about this:

a. use components from a single manufacture (ie sony alpine,pioneer,et al)
They all offered at one time a video display unit that can be linked and controlled
by another piece.

b. use different manufactures gear but have a single swither to control volume and allow
the ability to switch the audio between sources (ie kickers KQ5) without destroying them.

Hope this leads you in the right dirrection.

 

Back in the days I had 2 decks in the car, one tape and one cd. It was pretty awesome back then. I did it with a micro SPDT relay from Radio Shack and 3 sets of RCA Y adaptors to join the Pre-amp outputs from both the radios.

Joining the Pre-amp outputs does not harm the radio because I had it wired so that only one radio is on at any given time and of cause you have to have the default head unit which will control things. When I turn off the default radio the other automatically turn on so it worked great.

Just remember don't try to join the speaker wire outputs together, if you want to do that then you will need to do it with a switch. If you do it with a relay you will have some major electronic noise because I tried that way back and it did not work.