Holy crap audio people are such snobs, audio it's half truths half personal taste get your head phones, get a sound card and get a dac, and have a listen, keep whatever you like best, returning an item is not a big deal. At the end of the day it's you the one who will be listening to your equipment. I have a sound card at the moment, using the V-moda M100 and a cheap ass sound card with headphone amp that I've had for years, it's better than my onboard, it's also louder. I've borrowed my friends portable Fiio amp/dac and there is definitely a difference, my sound card colours the sound somewhat, it's not a matter of bottlenecks or best, it's about whether or not it's loud enough and personal taste. I like the sound i got from that relative cheap fiio e7; however, my sound card creative sound blaster something is not that far behind, and it's way better than my onboard. Personally i dont see the value in spending ~$250 on a dac/amp, but i can see myself replacing my sound card a few months down the line for a good value dac ~$100 ish. so just have a listen and see if you like what you hear.
Edit: my mobo is the MSI 890fxa-gd70