First step after attempting to contact the site's owners would be to issue their web hosting provider (you can get this from the whois records) with DMCA takedown notice, most hosting companies will comply if it's a legitimate copyright infringement and take the site offline. If the site is hosted by a reseller you then have to search their whois records and find out who hosts them and do the same.
Also if they have google adsense ads on the site you can issue google with a DMCA, google will usually block their ads loosing them revenue.