Im not expert here, but some things I did had catched.
Here is my try to add some 2 cents worths:
One big difficulty with urinary stones is they are of two different types. One is loving rather high ph, but the other prefer low ph... Thus, while low-ph food is often useful yes, as it helps against the most common urinary-stone. But it is no absolute rule, as some cats tend to develop the other type...
Of course, if your cat is known to have urinary-stone problems, your vet can tell you what type it is.
But there is another "remedicum".
Many experienced cat-people feels much of the stone problemacy is because many cats dont drink enough much. Ie, eating dry food, they should drink much, about 60 ml/ kilogram and day. As many cats tend not to drink enough, their urine is more concentrated then what is healthy - and - if they tend to get urinstones - they DO get urine-stones.
So the easiest way out is to simply give wet food of good quality (or BARF). Cats eating wet food do have enough with water, so it doesnt matter if they dont drink much.
Thus, no or seldom problems with urine-stones. They say.
If you do have a cat with tendencies for urine-stones, and want or must give it dry food as main food, then make sure the cat is drinking enough
(60 ml/kilogramme and a normal, not hot, day.
Ie a medium female cat about a normal glas of water a day, medium male a little more.)
Some sort of drinking fountain works often marvellously here! Even cats who dont like to drink water, tend to drink enough from a water fountain. (Drinkwell, Cat-It or other brands)
Or do have several watering cups around your place. Say 3 with fresh water, 2 with old stale water. As some cats want to drink stale water sometimes...
Oh, I think it was more then 2 cents... It seems to be more like a dollar worths... But I give you a price-reduction today!