Hoi! I use the Audioengine D1 24-BIT DAC and do very well with it!

Audioengine D1 24-BIT DAC (USB-DAC)

Hi
Your KRK Rokit 5 are active stereo studio speakers. Very good.
Since you seem to be into studio stereo and not 5.1 "surround", the Focusrite Scarlett actually makes sense for you vs. an internal Sound Blaster card.
Focusrite advantages:
Flexible USB connection for PC or notebook.
Microphone input XLR and jack

If you are planning to use a really good microphone with 48 V and XLR, then the Soundblaster Z is not enough.

I didn't know Focusrite before and I'm a bit surprised. They make really nice things :-)

I use the Sound Blaster Z myself for surround for gaming and watching films.
I've been satisfied with the Sound Blaster Z for years, and with the software under Win 10 as well.
The microphone input is also satisfactory, just only with jack and without XLR.
The sound goes to a Denon AV receiver with Klipsch speakers or to a Beyerdynamik MX300 headset.
Greetings