Different philosophies for different enthusiasts. If you have proper processing, you don't need it. It will only make things worse. Then again, if you don't, it may improve your listening experience. For some, the only way to do rear-fill is with the identical driver that you use for your front stage so as not to differentiate between the reproduction, ruining your image in the process. And even then, the signal should be run mono without amplification for the same reason.
Ultimately, you decide though. See what you lack and lean towards what you want.
I also don't like rear fill. The only time when it was slightly acceptable was when I had my Dolby Pro-Logic processing turned on, but Dolby is cheesey when you mostly listen to two channel sources.
Just buy some beer for that $35. There is nothing better than Saturday afternoon, garage, door panels off, Heineken and Marlboro After the install follows tweaking and listening to all the CD's one more time
