Hello Babel,
Feedback: Are you nuts? ;-) I mean regarding your comment to get rid of your Octatrack. Keep your Octatrack! That's a fantastic device and that can do so many things so easily (if you know how to use it, which I don't, but I know somebody who does) that if you want to get that kind of functionality in modular, I guess you need to reserve a pretty big part of your wall to make that full with modular then...
You could use the MIDI output on the Octatrack to a MIDI-in module in modular (unless your case got already a MIDI-in of course) and extract from that one the clock to keep everything in sync. The output of the modular back into the Octatrack and your Octatrack has such fantastic sample possibilities, I would use the Octatrack for sampling and not kind of in a forced way looking for a sample module in modular unless you really found the sample module that all does what the Octatrack can and more (and I doubt if it exists).
Other than that I think you are good on your way into modular and with keeping the advice of Ronin in mind, I think you should be all right.
Enjoy your system setup and don't you dare to sell that Octatrack ;-) Kind regards,
Garfield Modular.
For review reports of Eurorack modules, please refer to https://garfieldmodular.net/ for PDF formatted downloads