Layla has struvite crystals & infection.. Need future food advice!

[SolaMio]

Hi everyone.. Sorry I haven't posted in a while, I've been preoccupied with Layla (my calico ) who was having urinary problems... We took her for urinalysis and had her examined by our vet, and it turned out that she had/has crystals in her urine which have led to an infection. She was urinating anywhere she could in the house (as though she couldn't hold it) and seemed to be straining as if she was in pain. That was last week, and after a week on antibiotics she seems to be doing a bit better. I think she's on the mend

Anyhow, as part of her prescription my vet put her on Royal Canin SO 33 http://www.royalcanin.us/products/pr...il.aspx?ID=107
I know most folks here aren't big fans, and my vet recommended she be on another RC product "for life"... I don't have a problem with the 8 weeks on it for the sake of helping her get better, but I don't know about "for life". Can anyone recommend another cat food (I feed a combination of wet and dry) that would help prevent future infections? I was previously feeding California Naturals dry (Herring and Sweet Potato formula) and EVO cat and kitten formula for wet. Also I am concerned about feeding a really high calorie food (I know EVO is high cal, I only fed a little) since my other cat Millie is gaining a bit of weight lately (maybe a pound or two overweight), and the vet said that Millie could also eat the RC food during the treatment, but might gain another pound

Help!!