DNA Stratus or the Cayin HA 300 MK2. I have not heard either so I am wondering which would be better for me. They are in the same price range, any suggestion would be greatly appreciated.
I'm afraid I won't be able to help much because I've not heard the Cayin and I don't know your preferences. But I've got a Bifrost 2, like you (as I see from your profile page), and I have an African Blackwood Vérité that I drive from a Stratus. I love the combination.
I don't know if the Blackwood, in particular, contributes to these effects, but my VO is very hard-hitting, impactful, and has lots of slam. It's also lightning fast, generally, while also having pretty fast transient attacks. The leading edges of notes aren't overly sharp or incisive, but the Stratus works exceptionally well with these characteristics; its slightly warm, wet, and rounded sound takes some of the edge off the transients while retaining the overall speed of the headphones, and the macrodynamics and slam are preserved for the most part, without being quite as intense as they can be with other amps (I have a Schiit Mjolnir 1 as one of my solid state amps, for instance, and that slammin' amp's combination with VO outdoes even Focal headphones for macrodynamic strength).
While the Bifrost 2 helps with bass heft, the Stratus brings out the beautiful timbre of acoustic bass instruments. Quite frankly, I've not heard double basses sound better with other headphone setups. The Stratus also works wonders with the midrange of the VO. It's really very good. And the treble is lovely and smooth. The overall tuning is nice and coherent, and I love the timbre of instruments. The VO is a great all-rounder headphone from this chain. And It's a wonderfully engaging setup: there's some magic with this amplifier - lots of rich textures, that nice, slightly wet quality, top-notch resolution, and lots of lovely subtleties, as with microdynamics.
The Stratus does one last thing well: it provides a nice, spacious soundstage (the Stratus does this with dynamic driver headphones generally, including with my HD 800 SDR). Imaging, layer, and separation are all excellent and the expansive staging makes for a lovely open sound.
I hope this helps.