generally that is the best advice if you arent looking to spend money. trying out the speakers on your onboard is free and only takes a little of your time.
onboard audio ranges from quite poor to acceptable. even top end onboard is only about equal to low end soundcards. while quite true that a soundcard will be higher quality, whether or not you notice depends on your ears and the equipment you hook up. the soundsticks are good, but still are pc speakers and even if you used a soundcard i would not go excessive.
tldr: try out the onboard first. if you notice quality issues, static, buzzing, distortion then get a reasonably priced soundcard.