Thanks for the input guys....
I'm 5' 11"
Weight 158
Very flexible

Guess I kind of got hung up on the stack and reach numbers attempting to think they were the most important. But i see the points about bottom bracket heights and everything else pointed out.

Unfortunately, I'm buying used so just trying to get as close as possible to my current geometry....I would actually like a bit longer stem (currently 90mm)....the consequences of attempting this is resulting in a headtube that puts my handelbar drop to a point of discomfort. I'm currently on an effective toptube of 556 but as noted, would love to go down to a 545 effective toptube for longer stem length....this results in a bike with a) shorter headtube with too many spacers under it or b) a headtube that simply looks odd (lonnng) in proportion to the rest of the bike.

Anyhow....I understand now that the stack certainly is not as useful as I had thought it to be when making these bike comparisons.