Build me a perfect computer

[r3vbr]

Let's say I have a U$4000 max. budget for a computer with NO monitor.

I need to know what are the best components I can get for gaming and also multitasking a LOT.

I need at least 500GB of disk space and also a very FAST disk to read databases etc.

I bought a ZALMAN TNN case, and I want quiet components as well. So I was thinking of giving preference to an Intel CPU (wich I think has more stability).
http://www.quietpc.com/uk/tnn500a.php

Most important, show me a good motherboard
I need to know wich is the fastest DDR memory availible.
Video cards? Wich is the current best (or second best).
Is PCI Express good?
A fast Hard drive
Do I use RAID? do I prefer ATA or SATA? how about SCSI drives?

THanks for all your help!