Computer build from cyberpowerpc.com

Ok this is going to be my first gaming computer I have owned. I have spent SO many hours researching different information in preparation for this buy. I have even had to order computers then cancel them the next day because I find a cheaper place to buy from. I have ended up with two options buying from www.cyberpowerpc.com or building it myself. I want whatever is the cheapest and most convenient option. Here is what I am planning to buy from cyberpowerpc.com just want some last minute opinion.

CASE: Thermaltake M9 VI1000BWS Mid-Tower 420W Case w/ Side-panel Window

LED: 12in COLD CATHODE NEON LIGHT (BLUE COLOR)

Case Fan: Extra 3-Color Neon Light LED Case Fan 2 x Fans

POWERSUPPLY: 680 Watts Power Supplies (Hush Power Supply SLI/CrossFire Ready)

CPU: Intel® Core™ 2 Quad Q9400 @ 2.66GHz

CPU Heatsink and Fan: XtremeGear Ultra Heatpipe Cool Copper Heat sink CPU Cooling Fan 20dBA

MOTHERBOARD: Asus P5N-D nForce 750i SLI Chipset LGA775 FSB1333 DDR2 Mainboard

MEMORY: 4GB (2GBx2) PC6400 DDR2/800 Dual Channel Memory (Corsair or Major Brand)

VIDEO: NVIDIA GeForce 9500 GT 1GB 16X PCI Express (Major Brand Powered by NVIDIA)

VIDEO2: NVIDIA GeForce 9500 GT 1GB 16X PCI Express (Major Brand Powered by NVIDIA)

Hard drive: 500GB (500GBx2) SATA-II 3.0Gb/s 16MB Cache 7200RPM

CD: Sony 20X Double Layer Dual Format DVD+-R/+-RW + CD-R/RW Drive

SOUND: HIGH DEFINITION ON-BOARD 7.1 AUDIO

SPEAKERS: 600Watts PMPO Subwoofer Stereo Speakers

NETWORK: ONBOARD 10/100 NETWORK CARD

KEYBOARD: Razer Lycosa Black USB Gaming Keyboard

MOUSE: XtremeGear Optical USB 3 Buttons Gaming Mouse

XWNC: Zonet USB Wireless 802.11g 54Mbps Network Adapter

FLASHMEDIA: INTERNAL 12in1 Flash Media Reader/Writer)

If you would like to see what the other options are for components you can go to the website and click on mega special III.

Here a few questions I have that are specific:

-Is that power supply going to be enough to run my whole computer even if I overclock a little bit?
-Is that cpu cooler going to be enough?
-Is there a motherboard for about that price that will work better?
-Should I get those two 1gb Video cards in SLI or should I get one 2GB GeForce 9600 and get a second one later on down the road?
-This is a bigger issue I am debating with, should I get one 500 GB or two 500 GB in raid? Is there much of a difference? If I should get raid then what one what are the differences?
Is the data split between the two HDs automatic?
-Should I get a wireless USB network card or a wireless PCI network card?
-Would it be cheaper to get this system or a similar system built myself?
-Any other sugestions?

Keep in mind I have a budget. My MAX is about $1000 I already have a monitor and my system above is $981 with no tax or shipping and handling. It also has a 3 year warranty.
I know this post is very long but I want to make sure this is the best deal I can get so that I will be satisfied. Any contribution is helpful and I need responses as soon as possible like 5 days until I decide to buy that system.