No sound from speakers after stereo install, Sorry in advance for the long post! Options

[914zim]

Fellas:
I'll apologize up front for the long post... HELP!!
OK, I'm still having problems getting a new stereo hooked up in my 914.
The good news is I was able to mount the new stereo in the glove box area like the PO had set it up (see previous thread).
So, I have the constant 12V power connected to the memory wire, the keyed power to the main power wire on the stereo and the ground wire connected to the fuse block ground. The antenna cable is plugged int the stereo also. I have only 2 speakers mounted ahead of the doors in front, even though the stereo can drive 2 front and 2 rear speakers.
When I turn the key, the unit powers on and I can program stations and it holds them after I've turned the key off. I can see the little LCD meter jump up and down, so I'm pretty sure it's getting a signal.
The problem is I get no sound at all coming from the speakers.
The PO did mount an amp in the front which is what's confusing me. The amp has a terminal block for the speakers and they are connected to the speakers (I didn't mess with this at all). There is another terminal block called "high level input (l and r)", but there is nothing connected to it (never was).
There is also 2 RCA jacks labled "line input (l and r)". These were connected to the old stereo speaker connections, but when I connect the new stereo speaker wires to them, I get nothing.
My new stereo also has 2 RCA plugs coming out of it labeld "rch RED and lch WHITE" What are these for and where do they connect? I do not have them connected right now.
I've tried every combination of connections I can think of, but I can't get any sound.
Can any of you guys give me some ideas as to what's wrong here? Any help is greatly appreciated! Sorry again for the long post.
Andy...