The kia system has several issues that can not be fixed without an aftermarket dsp. If you look at my build log for my kia optima, you'll see the infinity systems stock frequency response, and how bad it really is.
edit, I didn't post that yet, I'll post it this afternoon. Fyi, there's a 40db broad peak in response in the bass/midbass.
What's worse, is that I'm not convinced you can get a full range analog signal from 6 channels, which would rule out most dsp'dsp's. The infinity system has a full 3 way active front stage, plus subwoofer.
I'll post more on the subject later today when I'm not on my phone.