I would personally go for a 4400 and overclock it slightly to the 4800, and beyond speeds.
2x 1gb sticks is better than 4x 512 as you can run the dual in 1T instead of 2t which the 4 sticks have to run in.
I would personally go for a single 7900gtx or a NVIDIA GeForce 7900 GX2 1024MB when they come out if they are any good.
If you want speed, and that was 8gb you had on there: http://www.anandtech.com/storage/showdoc.aspx?i=2480
Maybe you will change your mind on the drive: http://www.anandtech.com/storage/sho...px?i=2577&p=11
PCP&C are expensive and loud, it wouldn't be my choice, but great for the hardcore owner.