Thank you all for looking!
Northstar, I went the opposite route of what you did...I adjusted max 'Auto ISO range' to 51200. Also adjusted 'ISO speed range' to 204800. Not very useable at 204800 (as I've mentioned, I'm not a pixel-peeper nor a chart-shooter)...lots of color noise and loss of detail. In a pinch, sure. For the web, I wouldn't have second thoughts at 102400. In comparison, I wouldn't have second thoughts (again, for the web) at 51200 on my 5DM3. Northstar, when you get a chance, perhaps you can put your 1D X and 5DM3 through its paces based on my findings and validate or refute my observations. Thanks in advance.
Having said that, Northstar, I realize and understand why you chose to set max 'Auto ISO range' to 6400. Final exposure is, after all, dependent on shooting factors and like most everything photography-related, subjective. We all configure our tools to work best for our shooting style.