the ayc if its noisy is just a fluid change and is just £30 if you do it yourself as its easy on the 5 and 6's never normally any issue with box's or diff's some will crunch in 3rd but thats it , the main difference with e gsr and rs diffs is the gsr are case they sit in the gsr are weaker alloy to the rs are steal casing but you have to be a animal to break them in the gsr (sheady broke his at 550bhp+ by mad launching ) .Rust is a issue on the imports if not sealed regulary . oh to add the rs is a lighter car .Brakes are £140 for mintex or ferodo pads diskes about the same for bd ,clutches are around £400 for a stage 1 organic which will handle 350 bhp easily and will take around 4-5 hours to change