Help with choosing a new sound card

PC speakers are not like Home Stereo/Audio System. They are cheap, build and design for it's PC purpose.

Try downloading DFX: http://www.fxsound.com/dfx/index.php

Before you buy a sound card try adjusting your audio settings first, and remember all speakers require break-in. So your speakers may sound awful for a month or two but if you can wait until you got the components optimize, you may not need a sound card.

Some speakers requires longer to break-in than others.

Note that Logitech speakers tend to be muddy and the Creative speakers sounds more crisp than Logitech.

Definitely - Creative and Klipsch speakers are pretty good as computer audio is concerned, and then M-audio is among the best. Logitech has tons of power, but they are not known for their clarity.

Wow i'm impressed.. The DFX plugin made a dramatic difference when i'm listening to songs

Is there something that enhances the audio in general, instead of just a plugin for window players or winamp..ect.?

DFX - even with its limited control, it's the best free plugins you can add to enhance your audio that I've know so far. And a full version of DFX wont increase the quality as much.

Your sound chip comes with tone control so try accessing the equalizer on that, and player like the WMP or Winamp also comes with EQ.