Multi pay/subscription levels

Hi,
I need to know if there is a way to do the following with the membership plug-in.
1) my initial customer will pay for a basic and limited non-recurring subscription (let's call it 'warrior' level) from an initial offer on the warrior forum.
2) the customer needs to be able to login with a user name and password to access the info he/she purchased on the warrior forum.
3) once on the membership site, I want to give them the choice to upgrade their membership to a "premium" level to access additional material.

What's the best way to do this? I don't mind adding the warrior forum members manually, if I have to.
Should I create 2 separate sites? Need some advice...

Thanks,
Fernando