This is purely subjective and depends on your idea of "better" than onboard sound. What features do you need from an aftermarket sound card that your onboard can't provide? These days, unless you need a super high signal to noise ratio or other IO connections not available on your motherboard, most onboard sound solutions are pretty decent nowadays.
it is worth noting that most of us don't use a sound card anymore
if you use hdmi or displayport, your pc soundcard does nothing, the signal processing and generation is done by the tv ot monitor, so the sound card is useless this days under those circumstances