Update
OK. Finally got on the road with the amped stereo. As I said earlier, it's OK but not stellar. It works. I can say that. Am I impressed...not really. It just doesn't shine.
The line level converter (or the amp) appears to combine all the channels internally. When I attempt to adjust one channel on the line level converter, it has a major effect on the other channels. It took a bit of tweeking to get all the corners to sound the same. The music is there but it just doesn't sound any louder than the stock system with the stock speakers. It does sound more clear....but that's about it. The amp has the power to drive the quality speakers where the stock system just couldn't make the power needed.
Overall, it will drive the upgraded speakers. After this run with the Pyle amp, I'm gonna get the Rockford Fosgate amp. I'm honestly believing you get what you pay for. I paid $57 for the amp. It is a $57 amp. Yes, the RF amp isn't waterproof but I will rework my install to use it and I fully believe it will give way better results.
As a side note, one of my Polk speakers quit working on the woofer portion. I thought I had another issue with the amp. Turns out, the crossover had broken loose from the speaker. A little soldering and it was repaired.