Cheapest and best option, as the brakes should be up to the job, is a quality pad like EBC yellow, new standard discs (if they need replacing) and some really high quality brake fluid. Depending on how old your brakes are it not much to get the pistons and sleeves cleaned.
Cheap and really effective, failing that just bust out the big dollar and get the Brembo big brake upgrade - not sure on how this sits with the 17s though but looks mighty fine.