Comment on my ~$2100 gaming rig plan... and help choose videocard!

After a few weeks I decided to re-think building a new machine and came with the following specs: (I'm Canadian, so newegg isn't an option, and the prices listed below are next to lowest you can find in a CND store):

CPU: Intel Core 2 Quad Q9450
http://www.a-power.com/product-5176
$359.99
(plan to OC to about 3.2ghz)

CPU Heatsink: Thermalright Ultra-120 Extreme CPU Heatsink
http://www.a-power.com/product-3701
$64.95

CPU fan: Scythe 120mm Fan S-FLEX (1200RPM)
http://www.a-power.com/product-4283
$16.99

Mobo: ASUS P5Q-E P45/ICH10R ATX
http://www.a-power.com/product-6277
$174.72

Memory: OCZ Reaper HPC Edition OCZ2RPR10664GK 2X2G DDR2 1066MHz
http://www.a-power.com/product-5533
$134.99

Hard drive (2): Seagate Barracuda 7200.11 1TB SATA-300 32MB
http://www.a-power.com/product-4543
$195.99 x2 = 391.98

Optical drive: Pioneer DVR-215D Blk SATA 20x20 DVDRW
http://www.a-power.com/product-6065
$30.99

PSU: Antec TruePower Quattro TPQ-850
http://www.a-power.com/product-4216
$195.94

Case: Antec Nine Hundred Black 18.4"
http://www.a-power.com/product-2673-249-1
$99.99

And floppy for 10 bucks lol...

So far it totals up to $1481, leaving the biggest question, the videocard. I shortlisted the following options:

EVGA VC GeForce 9800GX2 SSC (675mhz)
http://www.a-power.com/product-6092
$574.97 (total would be $2056)

OR

EVGA GeForce GTX 280
http://www.a-power.com/product-6422
$649.00 (total would be $2130)

OR

2 x SAPPHIRE RADEON HD4870 512MB (in Crossfire)
http://www.a-power.com/product-6472
$314.72 * 2 = $629.44 (total would be $2110)

Unless I'm mistaken, the mobo I chose can support any of the above options. But feel free to suggest another one if you have a particular suggestion about videocard as well.

So which videocard should I choose? Also, is there anything you think I should add/remove/change? I plan the system to last 2-3 years. Already have monitor and other periphs.

Thanks for feedback! The cheapest x38 I found on a-power was:
ASUS P5E
http://www.a-power.com/product-4648
$249.76

I'll look at the sites you gave, the prices indeed seem quite cheaper.