Thanks
Thanks everyone who replied to my last post.
Given the comments, and my own research, Merc and I are going to PetCo today to read the labels and look for better food for our cats. I know to look for low magnesium, low ash, and we're going to put them on a partial wet-food diet (possibly even mixing water into the wet food to make it soupier, and force more water intake). And we'll stop leaving as much dry food out, measuring out what they ought to eat. (currently leaning towards "Wellness Complete Health" I read about on Consumer Search)
I'm surprised the vet suggested the diet they did, as quickly as they did. I had been expecting the vet to suggest part wet-food, as water intake seems to be the biggest problem, followed by particular minerals and pH balance.
After a conversation last night, I also wonder if having gone to a vet on Mass ave in Cambridge, the vet may be used to a richer crowd. And it's not so much that I'm against paying four times as much for my cat food (my cats have never been expensive to care for, and the price balances better when combined with less food intake), I was just surprised by that particular recommendation and I wanted to know what all my options were. Especially knowing that the top two ingredients in the brand he recommended are rice and corn. If I'm going to pay four times as much, I'd rather it be good. 'Cause it looks like I'll be paying four times as much if I try this wet+dry plan.

It's funny, Heisenberg has no problem drinking water. He's always taking a stop at the water dish. Guen seemed offended when I just tried squishing some of her treats into a plate of water to get her to consume more.

My next question, anyone have a vet recommendation? Hopefully someplace not too difficult to get to.