Its funny that most of you show you spec's for your machine and leave out what power supply you have.
most motherboards have the extra 8 pin for quads but most of all pc builders dont use the 8-pin.
They say you dont need it. If you dont then why is it there? point is that if its on the mainboard, then you have to use it for Quad CPU only.
If you not using it and you support this 8-pin on your main board. then thats the problem why your lagging. that 8-pin
gives the Quad the power it needs to the quad cpu.. if the dho head that built your machine didnt hook it up or insisted that you didnt need it.
Then its time you look elsewhere to get your parts.
Also anything above a QE666 Intel or 3 core AMD must have a DOT. rated 650 watt ps or above.. If its SLI then 850 watt...
I have a 1200 watt SLI in my machine.
Spend the extra coin to make sure your machine runs right.