Its all about what kind of all mountain riding. To me the sizes you are looking at are way too big. I ride a 154 Proto all mountain and 154 evo park at #175.
I realize there are many active members here who espouse larger boards.
There are also alot of eurocarvers throwing out advice, its important to understand the difference.
I ride the mountain like a skatepark, what some people call "all-mountain" is actually all mountain boardercross or groomer bombing.
I made a similar re-entry to the sport about 3 years ago at 34, you may end up with the perfect board - I didn't and its been a journey with bindings as well.
is it late october yet?