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!
A lot of times, in wall speakers are a free air design, meaning they don't like enclosures. You'd be better off starting with a DIY kit of drivers and build the crossover and encloruse yourself.
In that case, what's the best DIY kit for under $900?
I'm working on a Seas Thor right now. Got mine from ( carries it too)
I would check out "high efficiency speaker" forum and "loudspeaker" section. Browse, post a question, etc.

Also, for speaker kits and Fostex single driver speakers (like Omega speakers). They have plans for many of the Fostex drivers.

Warning diy speakers can be very addicting.
I recently heard a pair of Brines Acoustics FT1600 Mk II's. These were manufactured speakers that retailed for $900 plus shipping. They are also available as 'flats' (precut cablinet sections ready for gluing) and pre-assembled cabinets or just the plans for far less. They are a single driver design and sound as good as anything I have ever heard. I just ordered the flats. They are also very efficient. Too good not to look into.