yeah most of the monster class/race solutions in savage species are even too powerful to provide a balanced experience since most of their level-dependant benefits include changes to size, ability point increases, spell like abilities, etc.

the best way to incorporate catfolk into FR, as i don't think they exist as far as a basic, playable race, would be to create some cosmic or planar event in which the race migrated to the realms, as many of the others did in ancient history of the setting (elves, dwarves, etc never existed in the realms until they planeshifted or were brought by their respective gods)

i would simply make my own race, but if you don't know a lot about game balance in the 3.5 system, it's pretty hard to do. that and finding a place for these cat people would no doubt be difficult...imagine my small frustration when a player of mine once wanted to play an Avariel, or winged elf....they're supposed to be so rare that they're mythical beings IN a fantasy game hehehe