It depends. Many tuners run the AM audio through the same 75 µS de-emphasis as FM, causing a loss of treble response. In this case, installing the C-Quam decoder, and thus bypassing that audio filtering, can improve the AM audio quality quite a bit, even if no stations in your area are broadcasting in AM Stereo. For the pedantic: Yes, AM stations do use a pre-emphasis curve, but it's not as extreme as FM's -- it tops out at 10 dB at 10 kHz, instead of 17 dB at 15 kHz. Thus, even with a wideband detector, running the AM audio through FM de-emphasis will still result in it sounding dull.