Trying to split audio to headphone amp and Subpac, please help!

So I got this cheap Sabrent USB sound card so I could split audio to my headphone amp and a device called the Subpac and control the volumes separately on Voicemeeter Banana.

When I send audio straight to the Subpac (through the Sabrent) and enable it on Playback Devices, it works fine. Of course, this doesn't help me because then I only have the subwoofer vibrating, with no music.

However, it won't show up in Voicemeeter Banana for me to send audio to it. So I can get Voicemeeter Banana sending audio to my amp, but nothing shows up as an option in the USB slot where the Subpac is plugged in.

What do? I figure the problem here is that the app doesn't recognize the USB sound card as a sound card, so any sort of sound application that could accept it as an input which would be recognized as a sound device by Voicemeeter Banana would do the trick.