Hi, I have an IC24 and can say, with two VORs in the plane, I have never needed the VOR part.
Any scanner will be able to scan over 40 channels, so you can listen to hundreds of calls. By using an external aerial, you will cut out a lot of TV and computer interference, and receive stations many more miles away.
If you want to make your own aerial, a quarter wave vertical is 62cm long. (but not really critical to +-10cm.). Mag-mounts are useful as well for car or indoor use.