None of the OC apps/utilis I have used can auto tune the settings. Best bet is to yahoo/google your card and look for OC articles to get a good idea on the OC limits.
Also try the following sites:
http://hardocp.com
www.hardwarecanucks.com
www.bit-tech.net
www.overclock.net
www.tomshardware.com
www.overclockersclub.com
http://xtreview.com