There are several motherboards used in the G580 line... The particular motherboard installed into your system will determine what CPU upgrade path is available. Best option is to contact Lenovo Support via phone, ask them to help you find what works best for your system.
I do not work for Lenovo, I only provide suggestions based on my personal willingness to help others. All advice and comments are based on my experience, and do not reflect Lenovo policy, terms or conditions.