get the duel if you are plaining to upgrade in the next 2-3 years
what they are saying are if your planing on upgrading your system anytime soon after this go with the duel because it wont be as good as the quad in 3 years but its better then the quad right now just because a quad doesnt have very many programs that use all four cores
me personaly i would go with the quad it might be slower, but in the future it will be way faster then the duel,