I wasn't happy with the sound of my SC-901 (with subwoofers) until I discovered the Internal EQ. After increasing the low and high ends and decreasing the mids ("U" shape EQ) the sound is MUCH better then the factory preset. Here are the instructions from page 184 of the 2000 C70 owners manual:

B - Setting the internal equalizer
To select the frequency correction:

· Switch off the radio.

· Hold down preset button 2 (B).

· Switch the radio on again.

· Press button 2 until the desired curve appears : S70-V70-S40-V40-Custom.

Setting the custom equalizer (Custom EQ) - SC-901 only
· Select "Custom EQ" by switching off the radio, holding down preset button 2 and switching the radio again. Select "Custom" (see point B). · Press Scan.

· Press preset button 1-5 within 5 seconds:

Preset button 1 = set bass (60 Hz)

Preset button 2 = set mid-range bass (200 Hz)

Preset button 3 = set lower mid-range (800 Hz)

Preset button 4 = set upper mid-range
(3 kHz)

Preset button 5 = set treble (12 kHz)

· Adjust the setting by turning the Tune knob clockwise (increase) or counterclockwise (decrease). The change can be seen in the display, as well as heard.

· Use preset button 6 to adjust the settings of the front or rear speaker.

F = Front

R = Rear

Please note that the equalizer curves can be adjusted separately for the front and rear speakers.

· When you are satisfied with the adjustments you have made, press Scan again to store the settings.

· Press Scan once again to exit the settings mode.

· To select "Custom EQ", press the Volume knob.