Magnust... The advantage to calibrating for 8000K & 9500K are just what you mentioned. You can get a brighter image with more pop, more ON/OFF contrast, because you are moving higher than the D65 color standard.
I watch alot of content at higher color temps, so I like them to be flat from top to bottom of the luminance range just like 6500.
You might note my recent post on tweaking the Custom 4 color temp, which was meant to be the brightest output the projector could manage without WTW compression. The Factory settings were much too green, but dialing back green gain & bias, and balancing out red & blue, makes for a very usable ULTRA BRIGHT setting for the projector.
You have all the time in the world to discover what will work best for you. Enjoy. I look forward to reading more as you continue your journey with the HW10.