Welcome to the forum!

I know that my Sound FX external sound card returns a ruler flat response vs my on board sound chips in all 4 of my PC's and my laptop when I calibrated my REW software, so I say the card route would be the better way to go.

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70