I'm not sure how much you're into DIY, but I think you'll find the Pi speaker line at the top of the list. If you're not setup to cut wood, then maybe a local (amateur or professional) can help you out at a fairly reasonable price. If you're in or close to a big city then a Rockler or Woodcraft store would be a good place to look for a person to make the boxes.
Also, a local votech is another good place to get cheap work done. I think the kids there would love to build some big speaker boxes.....Colin