Hi,

Opera has a greater dynamic than pop : the difference between lower and higher is more important. If you want to have "more volume", compress the sound. The dynamic will be reduced : higher parts will be reduced and will be more close to lower parts, and after applying gain all the sound seems more strong. After it is a choice of quality... like mp3 vs Wav.

If you don't have a compressor in your software, use AUDACITY (freeware).

Regards