3.4sgpa and 3.6cgpa at a top 5 college and you want to do an SMP? lol, sheesh, but you don't need it at all. That's usually for folks with sub 3.0 gpa (science & cumulative) and/or where taking postbacc courses wouldn't have an impact at all. You would probably do more harm than good that route.
I would look at the school list that you applied to for last year, maybe it was too tier-heavy or something. Also, look into the secondaries/essays you wrote.
@Faha ?