From Denafrips Pontus to Lumin

@paoz  I'm using USB, only because I was already heavily invested in it and have optimized around it over the years.

If you have a choice, I2S is excellent as well as being a much less 'pricey' path.

is it better keep dac and streamer separate?

Pros and cons to both approaches.

THE Only Way for you to know is to bring in the Lumin and compare it head to head with your current front end source chain.

my Denafrips Pontus (with sotm 200ultra / sotm500 / sotm tx usb ultra)

What you have is very good. I recommend separating the sound quality/ performance choice and the convenience (all-in-one) choice and evaluate each on their own merits. There will be compromises / tradeoffs, no matter the outcome, and only you can make that call.

I’ve chosen to go with separate components for my source needs / requirements (computer audio front end) and have a mix of Small Green Computer / Sonore / SOtM / SR feeding my Denafrips Terminator DAC.

All the best!