It really, really isn't worth getting persuaded to buy expensive discs. Autolusso put their reputation on some pads - can't remember the make - that might be cheaper than DS2500, have a look at their site. Mine is currently braking better than it has done for years and I've just fitted the cheapest pads and discs I could find, Pagid and Mintex I think they turned out to be, from shop4parts or equivalent. However, what did it was replacing the calipers that were suffering badly from corrosion under the pad plates so they were badly seized - hardly bearing on the inner face of the discs at all. Bleeding/replacing fluid can also improve it a lot. Make sure all is working properly first otherwise it doesn't matter how much you spend on the pads and discs. If the inner faces of the discs front & rear aren't shiny then the calipers need attention.