I suggest you wait. Just wait. Intel is coming out with a new line (or recently did) of new cpus which are promising, their core2's have a really nice o/c ability, go to www.overclockers.com for more info, and sign up to their forums.
DX10 cards are coming out, and so is Nvidia's Quad-SLI! That driver needs one hell of a cpu to run its driver to coordinate 4 GPUs, so consider a fast dual-core. You could also wait and see if AMD makes their "reverse-hyperthreading" to make gaming 1337. If you want INSANE gaming, (an ultra-high res display is recommended for quad-sli, read up on tom's hardware forums)
RAM: MAX 2GB. And hope to god that 2GB RAM doesn't switch your memory controller to 2T timings, becuase that is DRAMATICALLY SLOWER than 1T. 8GB of RAM at 2T is still slower than 2GB at 1T.
HDD: if you Got the money, go ahead and buy those 15,000RPM cheetahs with perpendicular read/write as those are probably the fastest of the fast. Possibly in a RAID0. *Drools*
PCI-E is the only way to go if you want a 1337 graphics card, it allows faster speeds than AGP.
For your PSU, make sure it keeeps stable voltages. Get the 700w OCZ PSU. I have it. Works with my DFI Expert board which is really bitchy about current.
Mobo: Get one that is more than you need. You'll need it.
Make sure it's a good O/Cr. O/C runs my lyfe!
Audio card: XFI i think is the leader. But get your good speakers.
If you want everything watercooled, make sure your case will have alot of 5.25 slots, because you can watercool your HDDs when placed in a waterblock which can fit in the 5.25 slot. You an also get waterblocks for your RAM. But if you want the best of the best, once again; WAIT. just until next year. Then you can get a 1.5KW PSU from PC Power&Cooling and probably still need more power.
NVIDIA SLI KICKS ATI CROSSFIRES ARSE!
AMD KICKS INTELS ARSE MOST OFTEN. 2Ghz AMD ~ 3.5Ghz INTEL.
WATERCOOL YOUR VIDEO CARDS! USE COOLBITS TO O/C!
Have fun!
USB has a max rate of 480Mbps (bits) but shares it among ports. Firewire now has a version that maxes at 800Mbps, but most are still 400Mbps. This counts for each individual port as IRQs are not shared (i think)