Need Suggestions on PC Build

I'm working on building a bleeding edge computer and want opinions on this build please.

I'm working on a budget of about 6 grand and this comes in around 5500.

I'm most curious about the RAM and CPU.

Case: Thermaltake Kandalf VD4000BWS
Motherboard: ASUS Striker Extreme
Video Cards (x2): BFG Tech BFGR88768GTXWC37E GeForce 8800GTX 768MB GDDR3 PCI Express x16 HDCP Video Card with 3/8" Fittings
PSU: ENERMAX GALAXY EGA1000EWL ATX/BTX 1000W
CPU: Intel Core 2 Extreme QX6700
Memory (x4): G.SKILL 2GB 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400)
Memory Coolers: Thermaltake CL-C0026 RAM Heatsink
Desktop Memory Model F2-6400CL6S-2GBMQ
Hard Drives (x2): Western Digital Raptor X WD1500AHFD 150GB
Storage Hard Drive: Seagate Barracuda 750GB
Sound Card: SB X-FI
Keyboard: Logitech G15
Mouse: Logitech G5 2-Tone Mouse
Logitech G5
Monitor: Dell 24" (Already own)

Cooling is liquid. The case comes with Thermaltake 3/8" system. Pump 500 L per hour, 360mm X 120mm radiator with 3 120mm fans cooling it, 500 reservoir, and CPU block that I'll replace with a ThermalTake Volcano all copper CPU cooler with copper tubing and fan mount.
The video cards come with the liquid cooling already on them, just have to hook up to my tubing.

Main reason I picked the GSkill was that they're one of the few that have 2GB modules.

I guess the biggest questions that I have are:

1. How is ThermalTake for liquid cooling
2. Is the GSkill memory worth putting in a system that will only be moderately OCed (Maybe 3 Ghz)
3. Is the Quad-Core worth it given that the price difference between it and the c2d extremes is not that much?

The 4GB are in preparation for windows vista so I'm pretty sure that I'll need that extra memory for the resource hog that is windows. Just wasn't sure if GSkill was a decent brand. I usually use Corsair XMS series, but they don't seem to have 2GB memory moules.

This being my first liquid cooling system, are there any suggestions for a liquid cooling system better than the one that comes in the TT Kandalf Case? Here's a link to the case and the LCS that it comes with: Kandalf LCS Note: I will not be using the stock acrylic CPU cooler as I've heard those can tend to leak.

I can't find the CPU cooler I was planning on using right now, I'll have to post it when I get home. It's all copper, with a cooling block, copper tubing, and has a mount for an optional fan to blow across the copper tubing.