DIfference between onboard audio and 100$ sound card is 100-150% better... Than difference from 100$ worth dedicate sound card and 200-250$ worth is again 100% better and it's easy to notice difference even on excellent headphone and 200$ worth speakers. Simply on onboard sound card you can't recognize some effects at all. If you compare expensive dedicate and cheaper every sound is different and better defined. At the end if you compare onboard and expensive sound card it's same as you talk with someone in floor below you and in front of you. Sound is very important... And if someone tell you don't pay 200$ for sound card that's for expensive system... that's not true... all of these cards are gaming cards for games and few hundreds dollars systems and small number of people will use them on some really expensive systems worth few thousands... They don't use PCI-E sound cards.
Maybe investment in sound card is important because they last even 10 years, improvement in sound are not so often as graphic and you can use 10-12 years same sound card. Depend how much OS and drivers support, she will not be oudated and it's not wasting money, believe me.
Once when you used on good sound card she will follow you in all configurations... You will become opsessive with x1 PCI-E slot for dedicate sound.