IBEI strongly recommends that you open a bank account in Spain, especially if you are considering extending your residence permit after one year. There are many options and banks do not usually require much documentation.
You can walk into any bank and ask to open a bank account. Make sure you have some of the basic documentation you might need.
When opening a local bank account, make sure you have your ID/passport with you (if you have your TIE it will be preferred), as well as your IBEI acceptance letter and your empadronamiento certificate.