Looking for recommendations on a new system...

I have a $2000 budget to build a new gaming PC. I'm your typical gamer playing things like Battlefield, Vanguard:soh and I like to try out new games when they are released. I'll list what I've come up with so far and would really appreciate any comments or suggestions on the build. Looking to squeeze out the most performance I can.

All prices are from newegg.com
$79 Case - Sunbeam Transformer IATX Full Tower
$129 PSU - Antec True Power Trio 750W (SLI certified)
$315 CPU -Intel Core 2 Duo E6600
$219 Mem - GeIL Ultra 2GB DDR2 800 (PC2 6400)
$139 MB - ASUS P5N-E SLI LGA 775 NVIDIA nForce 650i
$778 Video - Dual Leadtek WinFast PX8800 GTS 640MB
$89 Audio - SB X-Fi XtremeGamer
$150 Drive - Dual WD 250GB SATA 7200RPM 16MB (Raid 0)
$35 Optical - Lite-On DVD Burner

(about $1900 total and I figure $100 gives me a little play for shipping, fans, cables , etc.)
A couple of questions:

How much performance increase would the sound card give over onboard? I currently use a Philips stereo with a USB PC link for games/music and a SB Audigy for my headset (Audigy is going to wife). Should I dump the SB X-Fi Xtreme and just use onboard?

Video Cards - These confuse me so much. I'm looking at dual 8800GTS cards with plans for the future and DX10. Is this worth it, or should I go with a single card or dual ATI setup?

This will be replacing a Dell XPS system I have been using for about 2 years now (going to wife since her PC is struggling with games). Current specs:

P4 3.2ghz
2GB
300GB (2x150GB SATA Drives RAID 0)
X800XT 256MB video
Sound Blaster Audigy
DVD-Burner


Any suggestions or comments would be appreciated. It has been about 3 years since I have built a PC.

There are a few things I would change.

1) Get a Single 150GB Raptor instead of the RAID-0. That Raptor will be much faster even w/o RAID-0 ($190 at NewEgg)

2) I would suggest an After Market CPU Cooler such as the Tuniq Tower. ($60+ NewEgg)

This would add about $90 to your build.
So where are we going to subtract to keep your budget in line?

Consider the E6400 which should OC to about 3.6GHZ with the TUNIQ tower and your 800Mhz RAM. This should make the overall cost slightly less but help performance.

Update:

Looks like this so far (changed a couple of things):

Antec 900 ATX Ultimate Gamer Tower Case
Antec 750 Watt PSU (SLI Certified)
EVGA 122-CK-NF68-AR LGA 775 nForce 680i
Intel Core 2 Duo E6400 (will overclock)
2GB DDR2 800mhz (G.Skill, OCZ,GeIL, or Corsair)
2 EVGA Geforce 8800GTS 640MB cards SLI
WD Raptor 74GB SATA drive
Seagate 320GB SATA drive (storage)
Lite-On 20x DVD Burner

Parts I will use from current system:
Logitech G15 Gaming Keyboard
Logitech MX1000 Laser Mouse
Philips MC-M570 (stereo system with USB connection)
Headset connected to onboard audio for FPS games

This will be replacing my Dell XPS system and the XPS will go to my wife (semi-gamer). The XPS is running a P4 3.2, 2GB memory, 300GB (2x150GB SATA RAID 0), Sound Blaster Audigy Z2, and an ATI X800XT 512MB video card.

I will probably upgrade the XPS' video card to a X1950 Pro card in a couple of months.