Hi Auygur,
Yeah, I think you should definitely broaden the list a bit beyond Harvard / MIT / Columbia! :-).... Darden doesn't actually accept applicants every year from what I understand, but this is what a friend of mine told me from the year he was applying.
More important than the GRE numbers are the percentiles, both seem fine for you but again you'll be competing, especially in strategy, with people that have perfect math scores (not so hard on the GRE) and very good verbal scores. An engineering degree with a good GPA is definitely nice, but I think there are people who have done research + have the basics in econ / psych / soc + good math, they are usually super-competitive for the top school PhD slots. But I think your programming skills, data mining, etc. will definitely help, lots of profs want to work with students with those skills as far as I understand.
I would definitely look at some mid-level programs in the US and Canada (e.g., BU, BC, University of Pittsburgh, Emory, FIU, UT Dallas, McGill, Simon Fraser, etc.) if you want to stay in North America. There are some really good programs in Europe as well (e.g., INSEAD, LBS, IESE, RSM, Cambridge, etc.) if you are willing to go across the Atlantic, those actually might give you a better lifestyle / options relative to the mid-tier in the US. I'm actually applying this year as well, but concentrating on European schools (have some friends who have said many good things, but also personal reasons).
But yeah, I would definitely look beyond the top tier, nothing is guaranteed there. Hope that helps!