I reckon current plan of heq5pro with 6" or 8" newt on top is a great one
And I don't think the 6" is a lesser option at all. Lots of DSOs will benefit from the slightly wider FOV and will be a slightly easier job for the mount.
For what its worth, I'm 4months in and started with the above with 8" option. I'm happy with that choice and I don't think I'll be getting rid of either the mount or scope anytime soon.
Perhaps factor in a coma corrector off the bat as well? It didn't take me long to notice and be bothered by the coma in my images. Baader mpcc seems a popular choice and gets the job done.