In need of a DAC / Amp that would work with my setup

Hey, so currently I have a pair of M-Audio AV40s which get a signal via a 3.5mm jack from my FiiO E10 connected by USB to my computer. The AV40s also have a RCA input which I have plugged in my turntable.

I’m looking to add a sub woofer into my audio setup. Since I can’t find one for around £100-150 with the two inputs, I’ve been looking at DAC/AMPs that have the functionality so I can plug in my computer and turntable and have it output to the sub woofer.

I’ve been absolutely tearing my hair out trying to find a DAC/AMP/Sub setup that’ll work with these AV40s.

Anyone familiar in this subject?

Many thanks,
Michael.

I assume so the bass and treble (wrong terms I know) can be separated by the computer.
I use a behrigher mixer & amp so don't ask me about audio.
Edit:
Something like this?


The setup would also depend on whether you get a powered sub or a non powered sub.