There's also a supplement called Cosequin that, while it was invented as a joint strengthener, also strengthens the inside of the bladder and urethra so crystals can't cause so much damage. Might be worth asking the vet about that too. How soon will you know back what kind of crystals they were, and which kind of food the vet recommends?

If they're struvite (ammonium magnesium phosphate) crystals, you can also get a urine acidifier (here's an example) supplement to help dissolve them. I've also heard that you can let a cat lick a spoonful of spaghetti sauce daily to bring down their urine pH! Never tried that, though. But it will depend on what kind of crystals they were - if they were calcium oxalate, you'll need to take a different course (one with which I have no experience).

Sammy is a beautiful fluffy boy, and I hope you get some useful information soon to help you take care of him!

Love, Columbine