adding I/O

[dzara 4]

Hello,

I recently acquired a small recording setup and was interested in expanding.
Currently, my chain is focusrite 220--fireface 800---mac
I was interested in adding some I/O at least 16 for now because I wanted to
purchase a summing amp, outboard and attempt some OTB.

My next purchase was going to be a Rosetta 800 because the 800 has adat outputs and the Rosetta Conversion

1. I know the fireface has a steadyclock , so should I just use the RME clock as my Master with the Rosetta, use the Rosetta 800 as the master or would I be better off buying an external clock like a Big Ben and clocking both off of that.

2. any other suggestions for further expansion of my I/O , taking a different route
with it would be appreciated.

Thanks