Thats correct, the quad core at the moment has no real benifit over the dual core in terms of price / performace ratio for general usage. The Quads will come down in price and by the time they do, we will see the full benifits of them.
3ds max 9, Mental Ray, do show a good deal of cut in render time but then can you afford 3ds Max 9, unless its your job. The Q6600 is still over double the price of the e6600 without double the performance in games and most appliations.
If you have the applications that will use the quad core then its made good use of. If your after the latest hype for the times, and have no real world usage for quad cores, then id say its your money, at least its future proof only your paying the high price in advance.
I havent gone Direct X10 yet as I have no use for it. When my card becomes slow in which I see poor visuals to run games, then I mite go DX10, but then the PS3 with the new mouse may stop that form happening.
. Being this tempory system has its limitations iv made sure I have nothink on this system other than security, Zbrush and Hexagon 2.1. I was in Zbrush yesterday and while it being slower than im use to, its rock solid. I wont overclock a system that hasnt had been primed and been fully tested for stability. The pc case is well ventalated and even this system, the components where well chosen, the gfx card wasnt part of this built BTW.