Advice on DAC/EQ to pair with HD 700s and Valhalla 1

Hey, I just got my first headphone amp, a Valhalla 1 for $50 that the original owner said he only used briefly before moving on. I'm really enjoying the amp but am starting to think about building a little stack. My only headphones are a set of HD 700s I got for cheap nearly a decade ago when no one wanted them.

I was looking at the Bifrost, but I am unbelievably confused about which one to look for and am having a hard time deciphering the options/upgrades for all of them (Seeing a lot of words like uber, unified USB, Gen X USB, multibit that are all flying over my head). Based on the prices I'm seeing I think a Bifrost 2 is out of budget. Any recommendations for which version of the Bifrost 1 would be best for this pairing?

I'm also interested in an EQ since the HD 700 needs some correction for the treble spike and I've found it annoying to do that in software. Thinking the Lokius is my only option since it's the right size to stack and has a 6kHz band.