PC Speakers & Chipset Sound Cards

the logitch system might give you some more "boomy" somewhat bloated bass and overall volume output over the bose sound dock. as far as quality is concerned it might be a bit better but its still only average. as long as you arent experiencing buzzing, crackling or distortion from your laptop output you're probably fine sticking with that as anything that is half decent for external soundcards is in the $50 range and i'm not sure you would want to spend that. if you did have issues with your onboard as noted above, you could likely fix it with a dirt cheap usb soundcard but its not going to be much better quality than what you have now (but it may get rid of any audio issues if yours is defective).

looks like the z533 is about $80 at best buy. for similar price you could get a pair of dayton b652's ($46/pair) and a lepai 2020+ amp ($30) and have a little decent stereo system. not sure how the current gen 652's are as over the years they have had a rocky road going up and down in quality but they should be better sounding than logitechs, but perhaps without the bass punch given no subwoofer. for a bit more you could get some mackie cr3 speakers.

if you want a subwoofer though, you wont find much better than the logitech set on a low budget.