http://www.autotrader.com/fyc/vdp.jsp?car_id=220300606&dealer_id=74718&car_year=2004&model=M3&num_records=100&make3=&make2=AUDI&start_year=2003&keywordsfyc=&engine=&keywordsrep=&certified=&body_code=0&fuel=&search_type=both&distance=300&model2=S4&make=BMW&color=&min_price=&drive=&default_sort=priceDESC&max_mileage=45000&style_flag=1&sort_type=priceDESC&address=14226&advanced=y&end_year=2008&doors=&transmission=Manual&max_price=40000&cardist=292
A bit cheaper and 6 speed wagon.