Slick, I'm so sorry to hear that Max has crystals. My Cirrus also has them and is on the dry c/d diet. He loves it but so do all of my cats so I have to make sure that they don't eat his food.
I hope he'll start feeling better soon. I think that my vet said that it could take about 3 months before you'll notice a change. Good luck and please keep us updated.
BTW if you buy the 20lb size it's cheaper. My vet will special order this size for me because they don't always carry it.