There are two types of steppings, A revision stepping and a production week stepping. The G0 stepping is a revision stepping that's in reference to the changes done to the chip. A Chip usually starts out at A0 or B0, etc, As time goes on the manufacture will make changes to the chip. A small change will result in A1, the changing of the number. a Large change results in B0, a change of the letter.
The reason some are going for a dual-core is because the Quad-core is kinda useless at this point. There are no apps or games out that take advantage of the extra cores. The choice is between a CPU that that performs better right now (e6850) or a CPU that will perform better at some unforeseeable point in the future (q6600)