Reading comprehension ! He is recommending Bose to cover up the holes only, not to use as outlets for sound.
Seriously, to the OP, is your decision to go in-walls purely based on the need to cover up the holes ? You might want to patch the holes and go with towers for the front, bookshelfs for the rear and a good subwoofer. Some research on AVS forum will do you a lot of good. If you decide to stay with the in-walls, try these (have a 30-day money back guarantee): HTD in-walls