Getting into Graduate School?

So I really want to get into a top tier graduate school (preferably Stanford) when I finish my undergraduate. I'm a dual Electrical Engineering and Computer Science major with an emphasis on Robotics. During my undergraduate, I've published two research papers at well known robotics conferences. I have one year before, and I currently have a 4.0 GPA (okay 3.98 because of a humanities course freshman year :P). I also plan on publishing at least one more research paper at the end of this summer. The reason I'm worried is that my undergraduate is being completed at a relatively unknown university (just barely top 200), it's ABET accredited and such. I'm just curious if anyone has any insight about how likely someone like me is to get accepted for a PhD with a payed research assistantship to a place like Stanford?