If you dont require a monitor i would stronly consider an X58/I7 920 unit...will take all of that $1000 but a superior unit. In the end the i7 will cost you about 100-200 bucks more.
That would be better, true. For example X58 can do Crossfire at full 16x+16x speed, while the GA-EP45-UD3P can't and will lose about 10% of the fps when used with HD 4870 Crossfire. Still, for that budget, I like his choices very much.
Antec 900 $110
GIGABYTE GA-EP45-UD3P $117
Sapphire HD 4870 1GB $245
PC P&C 750W $70
WD 640GB $80
Mushkin 4GB (2x2GB) $45
Total $887, and if you add Windows Vista Home Premium 64-bit $100 you end up with the whole $1000 budget taken.
Upgrading to i7 920 would cost something like: $300 (i7 920) + $260 (GA-EX58-UD4P) + $145 (DDR3, 3GB, http://www.newegg.com/Product/Product.aspx?Item=N82E16820231237) instead of $190 (Q6600) + $117 (GA-EP45-UD3P) + $45 (DDR2, 4GB). That's $353 more, not $100-$200. It's probably worth it, especially if he's sure he will add that second card.
Edit: nice work, grieve. I wouldn't downgrade the video card to 512MB, however.
Look, we all would like to spin up a nice i7, but realistically you could OC a Q6600 and it would probably do the job just fine. If you are uncomfortable OC-ing too heavily, you could find a 9550 which runs with a faster clock speed otb.
I don't think however I will be going with the i7. Even though I really want one, I can't spend more than $1000.
Is this a good build for a Quad?
Your build from the original post is very good.
If you change the PSU to the PC P&C S75CF it will be $30 cheaper and a little bit better, so do that.
If you can afford to add those two Xigmatek products that cmill0422 listed, do it, but you don't have to. You can add them later when/if you decide to overclock. Until you overclock, they will not bring you any real benefit. When you do overclock, they will let you reach higher clocks with lower noise and less chance of crashes.
If you prefer a cheaper case without lights get the RC-690 or the Antec 300. If you actually like the blue lights, check out the NZXT Tempest too. Same price as the Antec 900, same looks, huge, 6 fans.