The XR250 has a slanted front. It is done primarily to move the center of gravity back so the system does not easily fall forward. Not everyone wants to use sharp spikes on their floors to accomplish this. Some people see the slanted front as a means of adjusting the arrival time for the various drivers. It certainly doesn't hurt the arrival time, but it is already well within the acceptable limits.
Acoustic foam is used around the mid-range and tweeter.
The foam material reduces edge reflections at the higher frequencies and gives smoother response. The woofers are vibration isolated from the cabinet using cast aluminum mounting rings and foam tape. Our research employed an accelerometer attached to the cabinet in many areas. This indicates that additional internal bracing does not effectively reduce cabinet vibration. It only shifts the areas of maximum vibration to other areas that are not braced.