Disclaimer : Personally I've run both AMD/ATI and AMD/Nvidia Rigs in the past, this is my 1st Intel/Nvidia Rig since my 1st Pc a long long time ago.
I chose this set up due to it being the best on market build at the time for cost/power.

i7 2600k @ 4.4ghz
Asus Maximus IV Extreme
EVGA GTX570 @ 850/1700 / 1900
2xGTX260 (OC'd for Side+top Screens for EvE / 1 run PhysX also)
6GB DDR3 9-9-9-24 (need to improve that lol)
OS on 120GB SSD
Game is currently on HDD 10,000rpm **
Game Runs fine @800/1600 / 1900 (more normal OC for a 570)

Windowed
1920x1200
8x CSAA
Draw Quality 8
Background 5
Shadows: Highest
Ambient Occlusion: Off
Depth of Field: On (mostly still cant decide)
Texture quality: High
Texture Filtering: Highest

FPS 52-60fps General Field almost solid 60+
Occasional 40s in UL I think due to HDD more then anything (can update post moving it to SSD if you like)

Personally Id get the Nvidia again and Oc it.
But Any Of the cards at this level are great so I wouldn't over stress and get the best one for your system (cpu/mobo) or the best offer at the time.
You can always get better if you spend more money or SLI/Crossfire and so on.

Oh and Agreed about the Dell/alienware being lolfail priced.
People should build a Pc, its not that hard even for a 5yo these days..

* Best stable (light testing) 880/1760 / 2100 - need to finish making waterblocks for my system was a touch too warm for stable/more OC
**Will be moved to SSD in a day or 2 had tests to run before i moved any non crucial things onto SSD, can update then