Relax - I mean do the best you can to minimize the cat smells - but don't worry too much about it. We just went house hunting and must have looked at 50 houses - I would say at least half had a cat or cats and it usually it was fine. Most people will have carpets and draperies cleaned or taken out when they buy a house, so only dumb buyers wouldn't be able to see / smell past that.
I would be more worried about a kitty getting out and agree with putting them in one room, if possible, with a sign on the outside of the door. Many places we saw had the cats roaming free, and the selling realtors never seemed careful enough to us. Some would stand in the front door way with the door open, talking to us, with the "please keep cat inside" sign on it, so we would push our way in and close the door.
We always liked the friendly kitties, and some of the houses had nice features for them like big window sills and an out-of-the way litterbox area, that type of thing. Bear in mind many buyers have a cat or two themselves, so they won't be put off unless the house smells like pee or otherwise unkempt.
Oh and please don't use that Febreze crap - if odors are that bad, a good cleaning company needs to be brought in. I could always smell the animal and the Febreze, when it was used, then we would have to leave since it triggers my asthma. The houses that we immediately disregarded were the ones I couldn't even spend time in to look!
Good luck! Sounds like you are moving out of Texas.