I was thinking about getting another "Outlaw" amplifier. The Model 7700 (which I currently have because it has XLR inputs) and the Model 7125 currently list the chassis width as 17.2". One of the reasons I bought my Model 7700 is that it barely fits in my limited width 17.25" cabinet. I have measured my 7700 and its width is exactly 17.2" at its widest point which is the face plate.

The new Model 7140 says it has "a chassis which is the same size as the original 7125" but in its specifications the chassis width is stated as 17.5". Is it the same chassis size as the 7125 or is the new chassis really wider at 17.5"?

They are the same chassis size. They are both 17.25", looks like a typo on the 7140, we will make sure this is fixed.