Maybe I’m reading you incorrectly, but you can most definitely bypass BluOS and use Roon on the C-658 (and NODE). This is what I’m doing. Using the C-658 as a Roon end point and a Roon Nucleus (previously a MacBook as a Roon core).
I haven’t had to reboot the C-658, but I have experienced volume issues with the sub output with DIRAC not engaged. I’ve also experienced some clipping issues, but this was remedied by using Roon’s headroom management. In terms of DIRAC - mixed results and mixed emotions. I’ve found additional room treatments to be more my preference.
If this unit fits your needs, I’d say go for it, but I’d purchase from a dealer with a good return policy. In respect to the streamer itself, there’s better out there at this price point, but many fall short in features - especially if the NAD’s features are needed for a given setup. The one reassuring aspect is that this unit is continuing to receive updates which could potentially address the issues I mentioned.
Initially I thought your Yamaha was strictly an amp, but it looks like it’s an integrated. With the C-658 you’ll be putting a preamp in front of an integrated.