Extending 3 month F visa

Hi I would like to know if I can personally (i.e. without using agency) extend my 3 month F visa which expires nov 2nd 2011 for another 3 months? I know the agency can extend it for me for another 3 months. Will this be harder if I go to the office and apply myself? I have all the relevant documents already from my company.

Thanks for your prompt response. Nationality held is Australian.