i have a WRX rear sway sitting less than 3 feet from me as i type this. i don't know about your mounts, tho. if you find that it will work for you, you can have it. i also have my WRX springs and brakes. the rotors and pads had 7k miles on them when i upgraded. not the best brakes, but they would work well as an emergency replacement until upgrades could be afforded. you can have all/any of this stuff for dirt cheap. pm me if interested and we can arrange a meeting.
edit: i don't know the differences between the rs and the WRX. the springs and brakes may be the same as your stock parts.