I'm looking for the absolute best sound system (speakers) for my
laptop for listening to music (not gaming). I'd also like to know if
there is a way to plug it into a USB instead of the headphone jack
(without suffering quality).

In the past I've had the 4 speaker Klipsch promedia 4.1 (4 speakers
and 1 subwoofer). I had to plug the two channels into one adapter that
fit into the headphone jack. If Klipsch are still the best out there,
then that's what I'll go with. I would like to know if anything better
exists.

I've also tried the promedia 5.1, but the center speaker was wasted
since there aren't any adapters that can fit 3 cables (rear, front and
center) into a single adapter that goes into the headphone jack.  If
they now make adapters that will work with a center speaker, then that
might be a possiblity.

based on my experience, most laptops only equipped with 'generic' AC97
onboard chip to handle sound output, which is, IMHO, not adequate  for
those who has golden ears.

investing on expensive sound system won't do good if you're still
using that onboard chip. recently Creative has released a PCMCIA
version of Audigy soundcard for those laptop users who demand better
quality sounding. browse Creative at http://www.creative.com