Teppy, is leather out of the question? I have no idea what cats would do to it, but dog hair and dog slobber are easily cleaned from it.
I would do leather, but my vegetarian boyfriend is opposed to the idea, unfortunately.
Steph - if you do go slip covers, I find the canvas ones vacuum off cat hair pretty easily, and I scotch guarded fro mac spills which may help with the dog noses.
Yeah, I think that no matter what couch we pick, slipcovers are going to be the best choice for dealing with fur. I'm also going to get 5 or 6 lengths of fleece from the fabric store, to put in the spots where the cats like to sleep, b/c they'll grab the loose fur, and then I can toss them in the laundry.