I want to connect the NAD M10 V2 to my Marantz SR8015

Yes, You can connect the pre out of Marantz to NAD M10 V2 "ANALOG IN 1 or 2". Connect the front left and right speakers to the NAD.

1. Turn up the volume level of the NAD to 27dB (in order to obtain 100W max. output power), or to be on the safe side you can set it to a lower level (i.e. 20dB), but max. output power will be reduced.
2. Re-calibrate Marantz channel levels using a sound calibration mic via Audyssey Auto setup.
3. When you play any source through Marantz, just set the volume on the NAD to be the same as the calibration volume level. Use the Marantz to change volume and other adjustments.
4. Always remember to lower the volume on the NAD to normal listening level when you’re not using the Marantz!

You also can use an amplifier selector to do the job.

https://www.amazon.com/dp/B093GSS8P7

Thank you very much

I ended up using the Douk VU3 and it is working well to go between music (NAD) and home theater (Marantz)…