Caddy Head Unit

The following should be easy:

The 94 Caddy has the seperate head unit with the amp and radio in the trunk. Neither the CD nor the cassette works so am looking at replacing the dash unit. At the same time I thought it would be nice if I could also get the ability to play off a jump drive and maybe Bluetooth capability for my cell-phone.

My question is this: If I get a normal stereo with the RCA jacks in the back for pre-amp out, could I wire it up so that I can use the current amp and speakers and still have control from the stereo? Age and abuse of my auditory senses have rendered me deaf in one ear and with only 75% in the other.

I have no need to create a force three pressure wave inside the car nor do I wish to carry a 20 KW generator around with me to power my sound system. The current system works fine for me as all I listen to these days is talk radio and on long trips, audio books. Don't mind installing a longer antenae wire but would really prefer not to have to re-wire all the speakers.

Some insight into the current state of affairs in the audio world would be appreciated.

Bill