I feel your pain because I have a UTI kitty as well. He blocked up completely and nearly died 3.5 years ago and has been on the c/d ever since. If your kitty is on c/d, he must have had struvite crystals in the urine. One of the underlying causes of these crystals is urine that is not acidic enough. The c/d has special additives that help make the urine more acidic and it contains less of certain minerals that might promote the growth of the crystals. The other factor that promotes the growth of the crystals is dehydration. Most cats who eat only dry food tend to stay at a state of low-level dehydration. To address that, you might try some type of fountain to encourage kitty to drink more.
As for swapping foods, there are several OTC foods designed to help promote urinary tract health and generally they're geared towards struvite crystals since they're the most common. I know Purina One has one and Royal Canin does as well. I think you should be very cautious with that type of switch though. Ideally, you'd like to have your vet do a urinalysis before you start, after a week or two on the new diet, and then a few months down the road. The commercial foods might not be as effective as the c/d and you want to catch (and correct) and problem before it becomes serious.