Hello again, and thanks very much for your reply with additional information.
Wow, Beau has certainly been through a lot, with his urinary problems and surgeries, in the past 3 years!
It sounds like Beau is eating some good brands of food, now, and I completely agree with you, that the Hill's Science Diet prescription foods for urinary health (and all Science Diet foods) contain ingredients that are not *that* premium, plus, they include artificial additives and preservatives.
Crystal formation is usually prevented with a food that's low in ash. A grain-free food, would be best, XXXXX XXXXX feeding only canned food and having Beau drink a lot of water is the best way to avoid crystal formation. You can add water to his canned food, to get more fluids into him.
A nutritional supplement called Methigel, is a urinary acidifier, which may help. Always consult with your vet before giving any medication.
"Methigel Urinary Acidifier is a supplemental source of di-methionine and aids in maintaining a low urine pH. When combined with a proper diet, Methigel helps maintain a healthy, natural urinary tract."
Try to not feed any fish flavored foods, as these are also thought to contribute to crystal formation.
"It is far more important and beneficial to prevent alkaline urine by feeding a high protein/grain-free/low carbohydrate diet in order to minimize the risk of crystals." (Source: http://www.acreaturecomfort.com/cathealth.htm)
Please read the other information included at the link above, re: causes of crystals and bladder/kidney problems.
I'd stick with the Wellness for the time being, and try the Methigel.
I hope Beau will be doing better with his urinary health, by eating the more natural/organic foods. I also hope he recovers well, from this last surgery!