Help me decide on a new system

Pc3 and Pc5 are the only computers I would even think about buying. Pc3 is definitely the most powerful one there, it has one of AMDs bulldozer-eight core processors, which for that price, you cant go wrong with. Along with that it has the most powerful GPU out of all of these. I have a 6850, and trust me, there is no game it can't play on ultra when supported by a powerful CPU and 8 gigs of RAM. That is a great price for that desktop, I would recommend it. On the other hand you have the alienware. Mediocre CPU, mediocre GPU, mediocre everything. On the positive side, it looks cool. Now i'm not going to be a critic, but I would rather have my games looking cool, not my machine   . Don't worry though, you still should be able to play most games on high with that thing, and the case has plenty of room for future upgrades, though in the end it will still cost you more.

8120 bulldozer> i5 2130
6850> gtx 555 (its an overclocked 550)
8 gigs RAM (pc3) > 6 gigs RAM (pc5)

Overall, pc3 destroys pc5 in all but looks. Of course, the alienware can be tweaked for more cash to have equal the performance. Its up to you to choose what you want to do with your money  

Pc 2 and Pc 4 are the two best of that list and the reason being the Intel 2600 cpu. All of the choices have 8gb of ram and the other component are comparable but the Intel 2600 is the best cpu of those that are on that list and that is the core of your system. If you don't like the video card you can always swap it out for a better one.
The Intel Sandy Bridge has proven to be vastly superior to the AMD cpu's and for gaming you can't beat it. The only thing that will beat this i7-2600 is a better Intel cpu. I would get either 2 or 4 and look for a good deal on a top video card which will happen by the end of the week when the Nvidia Kepler is released. You will see some pretty good sales and rebates and you could end up with a video card much better then even the 6850 in choice #3. The two charts linked below will give you a pretty good idea where the cpu's rank and let you know also where the video cards rank as well.

http://www.tomshardware.com/reviews/gaming-cpu-review-o...

http://www.tomshardware.com/reviews/gaming-graphics-car...

go with pc number 3 for best gpu. go with 2 or 4 for best cpu. or build your own

There, fixed.

If he was looking to spend that amount of money because of having to upgrade, I would have recommended this :
http://www.tigerdirect.com/applications/SearchTools/ite...

Liquid cooling, cross-fired cards, touchscreen, i7 2600k. Blows any computer listed out of the water.   he wanted to spend 1000$ though, so that is not an option. Of course I agree with you on Kepler, I'm waiting to build another PC once it is released with the dirt cheap "outdated" Fermi architecture cards. He could actually wait and get better deals but of course that is up to him. As someone else mentioned a custom build would also work, assuming you are up to it.

http://www.newegg.com/Product/Product.aspx?Item=N82E168...
CyberpowerPC Gamer Xtreme 1322 (GX1322) Desktop PC Intel Core i7 2600K(3.40GHz) 8GB DDR3 1TB HDD Capacity AMD Radeon HD 6850 1GB Windows 7 Home Premium 64-Bit
$939.99

If you are willing to shop someplace other than Tiger Direct then you could take a look at this computer. It has the 2600k which is the unlocked cpu and it also has the 6850 video card. The price is under $1000 also.

I would take you 1grand and build your own PC. Use an I5 with a GTX 560 or amd equivalent yada yada... you can build a much better PC for the cash then any of those!!!!

+10

Loaded mobo too. I would definitely recommend this over the other options.

To answer your first question, today, AMD has no CPU's that can compete with intel sandy bridge for gaming in the medium and higher price point categories.
Read this article to get you started:
http://www.tomshardware.com/reviews/gaming-fx-pentium-a...

For gaming, the graphics card is the primary driver of higher frames per second and of being able to use higher resolutions and eye candy.
Buy a pc with the best graphics card you feel comfortable paying for.
Read this Tom's article to find out where you fit:
http://www.tomshardware.com/reviews/gaming-graphics-car...
My guess is that you should be looking at a card in the $200 range.

The $200 2500K is currently the best quad core cpu for gaming, bar none. It will perform on a par with the more expensive 2600K with a modest overclock.
Even the $120 sandy bridge cpu's like the i3-2100 dual core are good gamers.

It looks like you want to buy a pre-built pc. Have you considered doing it yourself? Once you have picked your parts, it is not so hard.

If you want a pre built, go to the site, directly, and configure your own with the parts you want.
I do not know which ones are good, and reputable. Perhaps a local shop that you trust will build one for you.

Left to default, you will be offered lower quality power supplies, and that is not the place to economize.

Ram is cheap, get 8gb in a 2 x 4gb kit.