'93 Sable Stereo confusion

Hi
Inherited a nice '93 from my in-laws. I am trying to install an aftermarket stereo and speakers, but crutchfield and I are both stumped. Conventional wisdom dictates that the car should have a non-amplified system, or the optional JBL system with a trunk mounted amplifier. I have a factory installed amplifier, but it is not JBL. I do have "premium sound" on the front speaker grills and "premium speaker" stenciled on the speakers. However, neither crutchfield nor several other sites deal with a hybrid system if you will. I found www.installdr.com which had a good discussion of the 91-93 systems complete with pictures of the connectors and amps, yet my system does not really match those either. I know completely the vehicle's history and know that it has not been modified from stock.

Have any of you dealt with the same issues? I hope to avoid a complete grass roots installation, but it may come to that, or give up and stay stock.

By the way, one more oddity: my rear speakers (and I assume my fronts) have 4 wires on the factory connector. What's up with that?

Bewildered.

Thanks

Well.......

Found a pretty good discussion of the issue here:

http://experts.about.com/q/Audio-Systems-835/Stereo-speaker-wire.htm?zIr=5#r


I think I'll probably just stay stock. Bummer.