Had some time this weekend to whip up another comparison with the bass 400. I didn't realize before the 800D had some cab sim based on the subway 15 on the DI when I did the first one, so to make it a little more comparable I downloaded the subway 15 IR on my captor x to use on the bass 400. I didn't try to get them sounding identical, but "pretty close" with a few basses, and then tracked some lines with a couple backing tracks.
For the part with the grabber, that is the natrual distortion from both amps with the gain cranked, I think on the 800D it's in low gain mode but dialed up higher, I didn't make drastic eq changes for the driven sounds, a little more HPF and maybe less low end on the 800D, left the 400 alone on the EQ but dialed the master a little lower (the captor peaks at one point, you'll see it glow red briefly). I don't think I'd run either amp dirty like that normally, I use pedals to achieve the distortion I want generally. Everything here was tracked raw bass > amp and no added processing in the DAW, so some parts could benefit from compression or whatnot, but that wasn't the point of this exercise.