Newegg.com - Acer X223Wbd Black 22" 5ms Widescreen LCD Monitor 300 cd/m2 2500:1 - LCD Monitors
Newegg.com - PC Power & Cooling S75CF 750W EPS12V SLI NVIDIA SLI Certified (Dual 8800 GTX and below) CrossFire Ready 80 PLUS Certified Active PFC Power Supply - Power Supplies
Newegg.com - ASUS P6T SE LGA 1366 Intel X58 ATX Intel Motherboard - Intel Motherboards
Newegg.com - Intel Core i7 920 Nehalem 2.66GHz 4 x 256KB L2 Cache 8MB L3 Cache LGA 1366 130W Quad-Core Processor - Processors - Desktops
Newegg.com - Microsoft Windows Vista Home Premium SP1 64-bit for System Builders - Operating Systems
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This will be a much better build than your AMD build and it is in your budget. It has room for an upgrade to SLI later down the road too.
Crossfire is basically the ATI version of SLI but that doesn't mean you can just stick two ATI cards in any board and they will work together or vice versa. The motherboard chipset has to support SLI or crossfire for the respective technology to work. The new x58 chipset for i7 has support for both SLI and crossfire.
The PSU I chose is a much better brand. OCZ can be a little sketchy on their PSUs. Some have fluctuating +12v rails which can cause problems. PC Power & Cooling is the best PSU maker around. They make a solid product.
EDIT: I don't know what you are talking about with the core 2 duos. They absolutely whooped anything AMD in their prime. They still beat most AMDs. I'm sorry but you are very very wrong about the core 2 duos.
This is what I would do:
Newegg.com - XFX HD-489A-ZDFC Radeon HD 4890 1GB 256-bit DDR5 PCI Express 2.0 x16 HDCP Ready Video Card - Desktop Graphics / Video Cards
Newegg.com - CORSAIR CMPSU-750TX 750W ATX12V / EPS12V SLI Ready CrossFire Ready 80 PLUS Certified Active PFC Compatible with Core i7 Power Supply - Power Supplies
Newegg.com - Intel Core i7 920 Nehalem 2.66GHz 4 x 256KB L2 Cache 8MB L3 Cache LGA 1366 130W Quad-Core Processor - Processors - Desktops
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That beats the snot out of any AMD build and it is well under budget.
understood.
The 4890 is probably the better choice. I didn't think of it when I made my build.
PC Power & Cooling is the best PSU brand around. I chose the red one simply because its a little cheaper but if you want a black one Newegg.com - PC Power & Cooling S75QB 750W ATX12V / EPS12V SLI NVIDIA SLI Certified (Dual 8800 GTX and below) CrossFire Ready 80 PLUS Certified Active PFC Power Supply compatible with core i7 - Power Supplies. Don't worry about the dual 8800gtx certified thing. It will run 2 4890s in crossfire if you later decide to do that.
The Biostar is also the better board but I was trying to stay under your budget and you will still do fine with the ASUS