[rick3000]

To be honest, it didn't take much effort, it just took a lot of time. It probably took me about 5-6 hours total, but I could probably do it again in under 2.5 hours. I didn't mind the time, and had some fun doing it.
To save time just make sure to be careful and precise with the dremel (hold it still, and cut straight and clean), and understand how to run the cable under the sill.

For me it was worth $130 just to get rid of the cubbies.
The rear speakers are a great addition to the Boxster sound system. It won't make a night and day difference in the sound, but it does make a noticeable difference. With the top down the the rear speakers are a great addition. It changes the sound stage to surround sound, from front-only sound.
So if you have some time, I would definitely recommend this for $130!

I also pulled the box out again today and added some polyfil from an old pillow. I packed it in lightly and then put some packing tape across the bottom of the box, to hold in when the box is removed. The polyfil doesn't help much, but since it didn't cost anything it's worth the addition.
Is it bad to have the polyfil touching the back of the speakers?