XPS 8000 Good buy? Upgradable?

Hey guys, I have a few questions hopefully you can answer.

I'm in the market for a new dell computer, something fast and I want to do some gaming on it.

I'm really interested in the XPS 8000 here are the specs. At Best Buy...

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Warranty Terms - Labor
1 year
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Product Height
16.1"
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Product Width
7.3"
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Product Weight
16.6 lbs.
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Product Depth
17.9"
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Gaming Series
Yes
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Processor Brand
Intel®
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Processor
Intel® Core™ i7
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Processor Speed
2.8GHz
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System Bus
NA
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Cache Memory
8MB
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System Memory (RAM)
8GB
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System Memory (RAM) Expandable To
16GB
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Type of Memory (RAM)
DDR3
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Hard Drive Type
SATA (7200 rpm)
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Hard Drive Size
1TB
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Graphics
NVIDIA GeForce GTS240 graphics
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Video Memory
1024MB (dedicated)
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Audio
Integrated 7.1-channel
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Speakers
None
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Network Card
Built-in 10/100/1000 Ethernet LAN with RJ-45 connector
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Wireless Networking
Dell 1505 WLAN PCI-E card with 11n mini card and external antenna
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Recordable DVD Drive
Yes, double-layer DVD±RW/CD-RW
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Recordable DVD Drive Speeds
Drive speeds not specified
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Direct-Disc Labeling
No
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Digital Media Reader or Slots
Yes, digital media card reader
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Available Expansion Bays
External: 1 (3.5")
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Available Expansion Slots
3
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USB 2.0 Ports
8 (2 top, 2 front, 4 rear)
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IEEE 1394 Ports
1 (rear)
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S-Video Outputs
None
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Serial Ports
None
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Parallel Ports
None
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Game Ports
None
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Keyboard Description
USB multimedia
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Other Control Devices (mouse, etc.)
Dell laser mouse
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Operating System Platform
Windows
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Operating System
Windows 7 Home Premium 64-bit
#
Software Included
Microsoft Works and more
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ENERGY STAR Qualified
No
#
HDMI Output
No
#
Blu-ray Player
No

It's an i7 8 gigs ddr 3 1tb HD, dual layer writes, gts 240.

Now I would really like to upgrade the graphics card to a gtx260 or so. The computer only has a 350w PSU. Will this work? On the Dell customizable site it allows you to add the card as an option so I am hoping I can.... Any thoughts?

Thanks.

P.S. Before I was gonna buy a customizable one on the Dell site, however it was half that computer 500HD 3 gigs ddr3 etc, but with a gtx260 for like 1k. So I can spend the same get better HD ram, wireless, just less on the graphics...

Thanks guys.