If you want more musicality, I would work from the software end. Uncompressed wave files will sound much more musical than the MP3's or the other compressed media. Unfortunately, that could be a VERY expensive upgrade if you have to buy the music again.
Otherwise, I'd go with the sub. A paradigm sub can be had used for under $200. Make sure that you get one where you can change the crossover frequency, as many designed for computer audio have a fixed frequency that is too high (120 Hz?). This would free up the atoms to be quite a bit more musical.
Otherwise, I'd go with the sub. A paradigm sub can be had used for under $200. Make sure that you get one where you can change the crossover frequency, as many designed for computer audio have a fixed frequency that is too high (120 Hz?). This would free up the atoms to be quite a bit more musical.