Need some advice with new pc for Gaming/Video editing

Hi, I'm planning to build a pc (would be my first desktop pc, I've always had laptops till now) for mainly gaming and possibly some video editing in the future
with the following components:

-Intel i920
-Motherboard Asus P6T
-3x2gb 1333 ram Kingston
-Nvidia GTs 250 1gb

but I still have some doubts.

-Should I get an i920 or an i750? (The cpu is the only component I don't intend to change for a long period so I would also like to choose the socket with more chances of future upgrading in order of not having to change my motherboard. I've also read in some places that the i750 is better for gaming but that would surely oblige me to update motherboard and cpu).
-I've heard that the i920 tends to over-heat easily, is it true? (I don't plan to oc it, it will remain at 2.66 ghz)
-Does the Motherboard P6T support having a nvidia gpu for graphics and another for physx?
-What power supply should I get? ( I don't plan to oc anything in my system, I will maximum put a dual gpu sli configuration or a gpu card only for physx rendering if possible, but anyway I don't plan to upgrade my gpu till directx11 appears in nvidia geforce series).

Thanks for all your suport and I hope your help will be usefull.

P.D: I'm sorry if my english isn't good, I'm spanish.