Male cat with soft stools

[SallyAnn]

In Dec 08 my 9 yr old male had a serious UTI and after a week at the vets and $1200 later came home. We gave him all the antibiotics etc.
The vet gave us some Science Diet kibble and said that 'your cat will only be able to eat this for the rest of his life'. (I can hear the sound of $$$$ coming from the SD rep!).
I put my cat back on his wet food and Wellness kibble.
He seems to have way more energy now and runs around like a kitten. He has no problems with peeing, but I have noticed that his stools are soft/runny. Not diarrhea consistency though.
The other thing that he has started doing is spraying (or attempting to) even though he is neutered. I know he was stressed out with the UTI and we have two other (female) cats, so thought this might just be a behavioural thing? He used to 'wiggle' before but it is only since the vet visit that he actually manages to get anything 'out there'.
He has NEVER sprayed before, and has never been sick either until this UTI.
Any suggestions on helping him get his stools firmer? I have read a lot of other posts and there seems to be so many but I don't want to end up making the situation any worse. Thinking along the lines of something I can add to his food??

[sugarcatmom]

He would probably benefit from some probiotics to help replenish the good bacteria in his digestive system that the antibiotics wiped out. Get some high-potency capsules from a health food store and mix a pinch in his wet food a couple times a day.

You might also want to seriously consider eliminating all dry food from his diet. It's the number one cause of urinary tract issues in male cats, even if it's the "good stuff" like Wellness. http://www.catinfo.org/