I’ve owned at one point or another every Elektron machine (excluding the SidStation) and I think you should get the Octatrack.

Everyone always says it’s difficult or confusing but it really isn’t. You can mangle samples to infinity, process external audio, and midi sequence other gear. It’s easy to quickly get a groove going with it, but will take a lot of experience to truly master all aspects of it. Considering you already have the Volcas it’s a no-brainer for me. It also pairs well with literally any other Elektron machine if you get a second one like you’re planning on.

I thought I could replace my Octatrack with Rytm because it can play samples, but it’s so much more of a hassle to use them on the Rytm than the OT. When considering the Rytm, don’t give it too much credit for it’s sample playback ability.