Advice on a new PC

[SharpeXB]

I would like some advice on putting together a new PC, my own skill and experience level at this is just above zero. That's why my first impulse is to order this retail rather than build it myself, I would have to pay CompUSA or someone to do that, haven't looked at what that would cost yet for comparison.
The goal is to be able to run Cliffs on full max settings at 60fps on a single 1920x1080 monitor
I would like to have a bit of future expansion capability in RAM and the ability to add another graphics card.
Thanks in advance for your advice.

Maingear Vybe Super Stock
(what leads me to the Vybe is it's size and weight. I am amazed looking at some other PCs like the Velocity Micro Z90 or the Maingear F131 that weigh 60-75 lbs! What on earth in a PC could weigh that much?!)

Motherboard: Asus® P8Z77-V LK Featuring Lucid Virtu MVP, CrossFire and SLI

Processor: Intel Core i7 3770 3.4GHz/3.8GHz Turbo 8MB L3 Cache HD 4000

Processor Cooling: MAINGEAR EPIC 120 Supercooler

Memory: 8GB Kingston HyperX DDR3-1600 (2x4GB)
(has the potential for 16GB but I hear 8 is enough for now)

Graphics: AMD Radeon HD 7950 3GB GDDR5 w/Eyefinity
(is this card enough or do I need two? I understand from reading forum posts that CoD needs about 2.7GB total)

Power Supply: 660 Watt Seasonic® X-660 80+ Gold Certified Modular Power Supply
(would like the ability to handle two of the above cards for expansion in the future)

SSD Caching: 45GB Corsair® Accelerator™ SSD Caching Drive

Hard Drive: 1TB Western Digital 7200rpm 32GB SATA 6G

Audio: 7.1 Channel High Definition Surround Sound Supporting S/DIF Optical Out

Microsoft Windows 7 Home Premium 64-bit

System is overclocked