Yeah from what I understand the Quad-core processors at the time, aren't LTE supporting, that is why we have dual core SIII's here, from what I understand though, T-Mo could have the quad-core, due to the fact that they use HSPA+, instead of true "4g" technology, but for whatever reason, they only decided to offer the dual core, but as previously stated, what kind of apps do we have that will really need a Quad Core machine at the time? Nothing...I mean the 2GB of RAM is a nice touch, but as previously stated, nothing worth getting your panties in a wad over.
IMO, when as previously stated, Jelly Bean is released with a Quad-Core phone, I might consider upgrading, because at that point, we might be looking at some seriously GAMING phones, or something insane at that point.
ADD: also, just to throw it in, AT&T is offering a RED SIII, for whatever reason, it's an exclusive for them....