Can you be more specific about the inputs into your active speakers and sub? Do they take unprocessed analogue line level inputs or do all inputs get digitised via an ADC? If the latter the benefits of the R26 will be limited, not nil, but limited.
Re high quality sub integration employing high and low pass filters with a high quality two-channel DAC this is not easy.
I bought a MinDSP Flex Digital to do this feeding s/pdif to the R26 and another DAC for the sub(s) which I thought didn't need to be as good as the R26. Even assuming differing DAC processing delays can be accounted for in the MinDSP (I tried my best) it was underwhelming - a poor cousin to the R26's internal HQPlayer NAA streaming endpoint. I also found that tweaks to the R26 chain significantly improved the bass (more controlled, textured, layered), so wouldn't want to miss out on that by using a more basic DAC.
An option I have considered seriously is a Passive Line Level crossover (PLLXO), such as the well regarded Marchand PLLXO. Active line level XOs by all accounts are less transparent, impose their own sig on the sound. After a lot of tweaking my system is now pretty resolving and balanced so that any tweak, even minor ones is audible. So I fear any line-level XO, even a passive one, would impact it negatively so never quite got around to ordering the Marchand PLLXO. In the meantime, and it is not ideal as I'd prefer to use a high pass filter to limit the range of my stand-mount Sopras, but my workaround is simply to run them full range and use the sub's internal low-pass to integrate with its natural in-room rolloff. In practice though that does not sound as good as the Sopras alone so for music I mostly leave the sub switched off.
YMMV of course, sorry I can't be more helpful or encouraging!