I'm looking to purchase the Samsung Galaxy SIII as a stand alone phone - I don't want to purchase it along with a provider, term, contract, etc. I just want the phone itself.

Samsung stores only sell them through carriers, if I purchase the phone for the full 650 from Robellus, I will have to pay a $35 activation fee even if I want to take the phone somewhere else.

BestBuy only sells them through providers.

I checked Amazon, they sell unlocked Samsung Galaxy SIII's that, according to the system specs:
HSDPA 850 / 1700 / 1900 / 2100
GSM 850 / 900 / 1800 / 1900

I was told that AWS/1700 phones work on Robellus, as well, as WIND Mobile. However, I wasn't aware that a phone could be both HSDPA and GSM (I am a phone newbie when it comes to this provider BS). Will this phone work on WIND and Robellus?