I'll speak for my own system HD800 (unmodded) + DNA Sonett 2. Please consider the following statements as a personal opinion elaborated in my own context with my own ears. Consider what I say with a grain of salt. I obviously exaggerate subjectives impressions to make it understandable.
The fact is the Octave and the Caiman are surprinsingly close IMO. and It seems I could happily live with both in my HD800 system.
The Beresford Caiman mkiI (CMII) is more suited to the HD800 than the Beresford Bushmaster mk ii (BMII). I've no doubt
. Unfortunately my USB/SPDIF transport is Broken since last tuesday so I can't use the Metrum Octave and the Bushmaster right now. When I'll grab a replacement Usb transport I'll give you more direct comparison. So. I can only use the CMII these last days.
From memory, the BMII is impressive but its sound is a bit too thin and there's some treble etch I dislike a bit with the HD800. the BMII was perfectly fine wth the ED12 + O2 combo though .
The CMII is a whole different story. Still very resolving with a great soundstage ( Beresford home sound I guess ? ) but with an overall more natural and bodied sound. I'm not sure yet but the CMII seems to hit the sweet spot for my tastes : enough overall body & bass slam to be enjoyable for Jazz and EDM and Orchestral music. enough clarity and bite in the treble to make classical Music exciting and energetic (THks for Chailly's beethoven ring .. it's exactly what I'm looking for bud !! ) . Mids are undoubtly less meaty and full than the Octave but remains "right" . I really loved the Metrum Octave but IME, with the metrum I listen more to EDM and less to classical which I found a bit boring (still with the Metrum) and the feeling of lack of Clarity never left me.
If I shoulds sum up and if someone would ask me some advice I'd answer that for pop/Metal/EDM/vocals , the octave is better. For Classical : Caiman mkII would be my pick. for contemporary Jazz ( stuff like Joshua Redman, Chick Corea, ACT recordings) : I enjoy both equally. Metrum sounds thicker and maybe a bit darker/warmer, Caiman sound more airy and neutral while staying musical . BMI is both detailed and musical too but with less meat on bones. Hope you see the point.
IMO both Caiman and Bushmaster HO are crap. So I only use those DACs with external amp ( Objective 2 & DNA Sonett 2)
I'll know a bit more after a few days without the Octave. My brain will be used to the Caiman mkII and reunification with the Octave will be insigthful. Time will tell.