<p>Ah, sorry, for some reason, I thought you were going for med school! Mea culpa. 
But yeah, I’m pretty sure that the same thing holds true for business schools: high GPA/high GMAT/work or research experience are much more important than the name of the undergrad school. And if you’re getting 680 - 690 on your mock tests, you’re off to an amazing start! 620 is usually the cut-off for top business schools, so you should have no problem at all. Good luck! ^_^</p>