Hello Darren,
well first of all any rs4 is no cheap to keep on the road, especially the brakes or engine, maintenance is going to be expensive, but the first place I would look would be the 7 ZAP site, thats the same site audi use, there you will find the original part numbers, just enter your details, from there with the part numbers search the sites, ie (auto doc) to find and compare prices, I found my kinetic discs at (atozwakefield) they have a site on Ebay, prices are good, if you can't find what you want send them a message, I did and I also got a better deal. There are lots of choices from other places, when you have the right part numbers from the 7 zap site, just search the net as I do, have fun siting on the laptop for hours as I did, good luck.