[linux-audio-user] amplifiers

I hope you'll forgive me if I ask a *really* basic question. I'm running a mix of Debian stable and testing. Kernel 2.4.18. I have a Creative Ensoniq AudioPCI sound-card. I'm using the OSS kernel drivers, but working up to switching to Alsa. I want to get better audio output---partially just for listening but also because I'm doing more and more recording. I don't do games. So for audio reproduction it's mainly a matter of DVD playing (opera and jazz mostly, some rock). I use Xine for DVD playback; I also use Ogg123 and Xmms for pure audio. So my very basic question is: how necessary or how advisable is it to put an amplifier between the audio output jack and the PC speakers? Has anyone got a recommendation for a good mid-range or mid-price amplifier that would make a noticeable difference? Thanks a lot for your time, Jim