Volume is at max, EQ is off. It is still quiet with volume levelling on (set to +125dB with anti-clipping on) or off.
Here is what the MM output (left) looks like compared to WMP output (right) for the same track. The actual MP3 waveform is the same as the WMP output.

It's not just with this one track but all tracks.
Increasing the preamp in the EQ even just a little bit makes the track clip and sound AWFUL.
Any ideas?