Building your own enclosures

I'm looking into buying new speakers, and I can get great discounts on in-wall speakers. I was wondering if anybody has had experience with building enclosures to make in-wall speakers into a floorstanding form? My main concern is sound quality, but I have a lot of experience in furniture building and am fairly confident in building an MDF cabinet to mount the speakers. The speakers I am looking at are the new Infinity CAS 3.1. Also, suggestions for the cabinet design are welcome!