Front speakers?

Hey, Earlier today me and one of my friends who knows a decent amount about sound systems and electrical wiring ect. Installed some subs and an amp in my 2000 impala. Since we couldnt use the stock stereo for the rca we tapped everything into the stock amp and used a line output converter for the rca cables (my impala has the premium sound system or w/e where it has an amp) and we ran everything through there. Everything is working except now the front door speakers dont have any sound coming through them. We double checked and we are pretty sure that we did not cut those wires back by the amp. The only thing we were somewhat thinking is when we unplugged the battery to hook up the power cable for the aftermarket amp, if somehow when it came back on its not reading the front speakers or something.. I honestly have no idea what it could be at this point we tried everything we could think of so far. If anyone knows how to fix this, or has any good suggestions on things to try and see if they fix it, please let me know.

Thanks,
Tom

Is the new sub amp running off just these 2 channels, or all 4?

Do the Subs hit?

Is the RCA converter hooked up to "low Level" input side of the amp, or is it connected to the "high level" Output side of the amp?

the converter is mostlikely designed to draw on "high level" or the powered side and could draw all the signal away from the stock amp if it is connected to "low level" before it hits the stock amp leaving no signal.
if this is the case, moving your converter to the output side of the amp should remedy.

I also hope you ran a new fused power line and ground for the sub amp, and not used the stock connection or you are asking for a fire. I only say so because i have seen this fatal DIY mistake many times.