When introducing my dogs to my ferret, which Iknow is different, but still somewhat similar, it was much easier tointroduce the older dog than it was to introduce a puppy. The puppyjust wanted to play and bite and wrestle, and the ferret justifiablydidn't care for that.
I feel like a kitten may be the same way. Playing a little to rough forthe bun... but with an older cat you might also get a kitty who isintolerant. But if you talk with the rescue I'm sure they can recommendan older cat with a mellow personality. That's also the benefit ofgetting an older cat at a rescue. They know the kitties' personalitiesand can help you find one that's right for you!