I have no experience of TRW parts, but I did replace all discs and pads with ATE items on our previous 9-3 Sportwagon. The total cost including VAT from C R Marks was only about £150. The performance of these parts was excellent and for example the mileage covered by the rears, up to the time I traded the car in, by far exceeded that of the previous genuine ones I had fitted not long after purchasing the car. I cannot see, without dismantling, if the current car has genuine parts or not but they will be replaced within the next few months. At present there is an annoying low pitched squeal, when crawling along in D, each time I release the brake pedal. I reckon there is possibly a bit of glaze on the pads. We will see what happens when I fit the new ones. ( I realise this may be a 'feature' of the auto vehicles)
HTH
Pete