A:AnswerThe $550 one has a slightly faster factory overclock, so it's a little faster, but not by much.
One has a 1785 MHz boost clock, and the other goes up to 1815, so just a little faster.
A:AnswerAn equivanlent can be found on NewEgg if you want to buy this product. It is being sold for the same cost ($499.99) so it shouldn't be much of an issue