100.3 has a broadcast radius of 76 miles.
You can check the signal strenth of KMXD for your zip code here, although it only lists zip codes getting 50+ dBu: http://www.v-soft.com/ZipSignal/default.htm
76 miles isn't entirely true. KMXD is essentially interference-free for between 60-75 miles from Alleman. It's been reported that the 100.3 signal can be picked up in northern Missouri and far eastern Iowa. I can get about 100 miles from Ames to the NW before the signal starts to diminish.
I think this change is a great thing, especially for events at night. There are spots in Ames that I can't get KXnO...in my car...during the day! At night, forget about it! Now, with a powerful FM station that isn't forced to power down at sunset, a much larger area will be able to hear the nighttime FB and MBB games.