Nice Parts, most people think a Quad core cpu is not worth it, but they will notice a immediate improvement over a single core, you did not say which model of I7 so I am guessing the 920, a Great Video card to Massively Increase your Video/FPS Performance would be the GTX 260 or Higher
I thought about getting GTX 275, but I could wait for the GTX 300.
New Parts
Intel Core i7 920 Quad Core Processor LGA1366 2.66GHZ Bloomfield 8MB LGA1366 4.8GT/S
Gigabyte EX58-UD3R ATX LGA1366 X58 DDR3 2PCI-E 2PCI SATA2 RAID Sound GLAN CrossFireX Motherboard
Corsair TX750W 750W ATX 12V 60A 24PIN ATX Power Supply Active PFC 140MM Fan
Corsair XMS3 Dominator TR3X6G1600C8D 6GB DDR3 3X2GB DDR3-1600 CL 8-8-8-24 Core i7 Memory Kit
I was worried about the Video Card not fitting as a GTX 275 is 10.5M and my Case length is 10M (with the HDD rack).
During installing, I notice the PSU is slightly smaller to the width of my case.
Other than that, the extra cables are currently using the free space of my ROM slots.
But no one has answer my first concern.
WHAT THERMAL GREASE?
I asked around and its possible that its underneath the FAN for the CPU, because I did notice a yellowish plastic or jello.
BTW,
I've never used THERMAL GREASE on my AMD CPU and it still been working for 3 years!