@Ralph-Janssen Sorry for the delay in replying - I have been out travelling! I think you will find that 800 nits will be a significant improvement the 500 nits you have now. My older Garmin XT396 is 700 nits, for example, and it is bright enough although it gets washed out in bright sunlight. The Zumo XT is 1000 nits is noticeably better than the 396. I don't have one of those, but several friends do and they report that is bright enough for any conditions.
Vinnie