Compressing Music Files

[YAY_WOOT_YAY]

If say... I have an MP3 format, Final Fantasy music, and i want to reduce/compress/(anything that'll make size smaller without cutting the music too much) the file size so in Warcraft 3 it wont lag game up... How do I do it?

NOTE: (I have used sonis stage mastering studio to cut some parts out to reduce it to around 711 kb)

A filesize below 125kb would be really good .