way to increase volume.

[SouthPole1989 0]

hi, i have been using my psp for music lately and the difference in volume from a cd and that is huge and i am wondering how can i go about making it louder? i figure i might be able to use a linedriver but then i got to thinkin that might mess stuff up since most are 8 volt line drivers so if a head unit only has 4 volts preamp i can see problems. so can only one shine some light on this. of btw i am getting a Alpine CDA-9885 ( i need a decently cheap but still a decent headunit right now.)