Dude I think you should just buy the gtx 560.... you've got a bunch of games, it'll end up being cheaper for you and your brothers will get a better card as well.
Just save up afterwards and wait for the right time to get a PS3. From the sound of it you are more into the single player experince and maybe local co-op, so it won't matter if you get a ps3 now or next year cause the single player experience will always be the same.
Hope that helps....







