Help With DSP Options

I’m looking into trying some DSP, but not sure what’s out there that fits my needs. I want to keep the signal digital till it reaches my dac.  I also need the DSP to output over usb. This is where I’m having trouble finding something unfortunately. I can find a few products that keep the signal digital but none that output over usb. I don’t have a large budget right now, around 500$.  Still interested in hearing about more expensive units though. If out of budget but otherwise the right fit I’d be willing to save for a bit before purchasing. Also curious peoples thoughts on how a DSP might impact the sound outside of its DSP capabilities. I don’t want to loose transparency by adding the DSP, so hopefully that’s possible. Looking forward to what you guys can come up with.